training manual VOLUME 1 STEP 3 / TCCS (TOYOTA COMPUTER- CONTROLLED SYSTEM) FOREWORD This Training Manual has been prepared for the use of technicians employed by Toyota's overseas distributors and dealers . This manual, "TCCS (Toyota Computer-Controlled System)", is Volume 1 of the thirteen Training Manuals which constitute Step 3 of the program of skills which all Toyota New TEAM* technicians should master. It should also be used by the instructor in conjunction with the accompanying Instruction Guide . The titles of the New TEAM Step 3 Training Manuals are as follows : VOL . TRAINING MANUALS VOL . TRAINING MANUALS 1 TCCS (Toyota Computer-Controlled System) 8 NVH (Noise, Vibration & Harshness ) 2 Turbocharger & Supercharger 9 Fundamentals of Electronics 3 Diesel Injection Pump 10 CCS (Cruise Control System ) 4 ECT ( Electronically-Controlled Transmission) 1 1 Car Audio Syste m 5 Full-Time 4WD 12 Automatic Air Conditioning Syste m 6 TEMS & Air Suspension 13 SRS Airbag & Seat Belt Pretensione r 7 ABS & Traction Control Syste m It is not enough just to "know" or "understand" - you need to master each task so that you can do it. For this reason, theory and practice have been combined in this Training Manual . The top of each page is marked either with a Q symbol to indicate that it is a Theory page or a® symbol to indicate that it is a Practice page . Note that in regards to inspection and other procedures mentioned in the Practice section, this Training Manual contains only the main points to be learned ; please refer to the relevant Repair Manual(s) for details . The following notations often occur in this manual, with the meanings as explained : A potentially hazardous situation which could result in injury to people may occur if CAUTION instructions are not followed . NOTICE Damage to the vehicle or components may occur if instructions are not followed . NOTE Notes or comments not included under the above two headings . Information not required to pass the TEAM certification, but which may be useful t o REFERENCE instructors and to trainess who wish to gain a deeper knowledge of the subject . *TEAM : TEAM stands for 'Technical Education for Automotive Maste ry', which is a training program divided into three steps according to the technician's technical level . This program makes it possible for technicians to receive the appropriate training for their level in a systematic manner so as to help them achieve the skills and efficiency of skilled technicians in the sho rtest possible time . This Training Manual explains the TCCS engine control system based on the 4A-FE engine . However, representative engines other than the 4A-FE engine have sometimes been selected to explain mechanisms not found" on the 4A-FE engine . In this way, explanations of as many mechanisms as possible have been included . All information contained in this manual is the most up-to-date at the time of publication . However, we reserve the right to make changes without prior notice . TOYOTA MOTOR CORPORATIO N ©1997 TOYOTA MOTOR CORPORATION All rights reserved . This book may not be repro- duced or copied, in whole or in part, without the written permission of Toyota Motor Corporation . TABLE OF CONTENTS Page ABBREVIATIONS AND ECU TERMINAL SYMBOL S ABBREVIATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1 ECU TERMINAL SYMBOLS . . . . . . . . . . . . . . . . . . . . . . 2 OUTLINE OF TCC S WHAT IS TCCS? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5 HISTORY OF TCCS ENGINE CONTROL SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 SYSTEM DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1 . Functions of engine control system . .. 8 2. Construction of engine control system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3 . Engine control system diagram . . . . . . . . . 1 2 ELECTRONIC CONTROL SYSTE M GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 POWER CIRCUITRY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 1 . Engine without stepper motor typ e ISC valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2. Engine with stepper motor type ISC valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 VC CIRCUITRY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 GROUND CIRCUITRY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 MANIFOLD PRESSURE SENSO R (VACUUM SENSOR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 AIR FLOW METER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 1 . Vane type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 2 . Optical Karman vortex type . . . . . . . . . . . . . . 21 3 . Hot-wire type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21- 1 THROTTLE POSITION SENSOR . . . . . . . . . . . . . . . . 22 1 . On-off type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 2 . Linear type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 G AND NE SIGNAL GENERATORS . . . . . . . . . . . . 24 1 . In-distributor type . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 2 . Cam position sensor type . . . . . . . . . . . . . . . . 27 3 . Separate type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 WATER TEMPERATURE SENSOR . . . . . . . . . . . . . 30 INTAKE AIR TEMPERATURE SENSOR . . . . . . . 30 OXYGEN SENSOR (02 SENSOR) . . . . . . . . . . . 30- 1 1 . Zirconia element type . . . . . . . . . . . . . . . . . . . 30-1 2. Titania element type . . . . . . . . . . . . . . . . . . . . . . . . .32 LEAN MIXTURE SENSOR . . . . . . . . . . . . . . . . . . . . . . . . 33 Page VEHICLE SPEED SENSOR . . . . . . . . . . . . . . . . . . . . . . . . 34 1 . Reed switch type . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 2 . Photocoupler type . . . . . . . . . . . . . . . . . . . . . . . . . . 34 3 . Electromagnetic pickup type . . . . . . . . . . . . 35 4. MRE type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 STA SIGNAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 NSW SIGNAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 A/C SIGNAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 ELECTRICAL LOAD SIGNAL . . . . . . . . . . . . . . . . . . . . 39 FUEL CONTROL SWITCH O R CONNECTOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 EGR GAS TEMPERATURE SENSOR . . . . . . . . . . 40 VARIABLE RESISTOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 KICK-DOWN SWITCH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 WATER TEMPERATURE SWITCH . . . . . . . . . . . . . 42 CLUTCH SWITCH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 KNOCK SENSOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 HAC SENSOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 VAPOR PRESSURE SENSOR . . . . . . . . . . . . . . . . . . . . 44 TURBOCHARGING PRESSURE SENSOR . . . . 44 STOP LAMP SWITCH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 OIL PRESSURE SWITCH . . . . . . . . . . . . . . . . . . . . . . . . . 45 COMMUNICATIONS SIGNALS . . . . . . . . . . . . . . . . . 45 1 . Throttle opening angle signals . . . . . . . . . . 45 2 . Throttle opening angle signals fo r TRC system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 3. Cruise control syste m communications signal . . . . . . . . . . . . . . . . . . . . 46 4. TRC system communications signal . . 46 5. ABS communications signal . . . . . . . . . . . . . 46 6. Intercooler system warning signal . . . . . 46 7 . EHPS system communication s signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 8 . Engine speed signal . . . . . . . . . . . . . . . . . . . . . . . . 47 9 . Engine immobiliser syste m communications signal . . . . . . . . . . . . . . . . . . . . 47 DIAGNOSTIC TERMINAL(S) . . . . . . . . . . . . . . . 4 8 EFI (ELECTRONIC FUEL INJECTION ) GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 TYPES OF EFI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 1 . D-type EFI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Z-L£ l . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II-080 9£1 . . . . . . . . . . . . . . . indlno leulwi a3 ldn J0 3A 'Z ti£L suolioun} dwel „3NIJN3 )103H0„ L ££ """""""""' 1f1d1f10 lb'NIWa31 l3n 8 0 dn (INb' dWt/l „ 3NIDN3 )103H0„ Z£ L"""' W31S AS 011SON OVIO 3O 3ldI0NI!!d L C L . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .lb'a3 N39 SISONJtJI O 6Zl IN31S)lS 1Oa1N00 IV 6Z l" * *"*'* " * . . . . . . . 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L 99 """"""""" f103 3NIJN3 30 SNOIlONf13 99 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . n I en J I b' Z 99 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A o a 33oj P9 I 41' L ti9 """"""""' W31Sl.S NOIlOf10NI HIV E9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ajlmono Z9 leoulaala Joloaful liels plo0 . . . . . . . . . . . . . . . . 4ollnns awll J010 a1ul MIS Z9 . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 o3 0aful 1iel s PIoO 09 """"""""""' sP043ew anl J p Jo33a 1 ul 69 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . sioloafu I 89 . . . . . . . . . . . . . . . . . . . . . . . . . . . j o;eln6aj ai nssa J d 85 . . . . . . . . . . . . . . . . . . . . . . . . . . . . j adwep uolleslnd 84 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . j aili} lend 99 . . . . . . . . . . . . . . . . . . . . . . . . . . . loixuoo dwnd land tr 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . dwnd le n d E9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0l '6 Z9 . . . . . . . . . . . . . 1=13 adAl-3 -Z a6ed Page DIAGNOSTIC CODES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138 FAIL-SAFE FUNCTIO N FAIL-SAFE FUNCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 5 BACK-UP FUNCTION BACK-UP FUNCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 TROUBLESHOOTIN G GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 HOW TO CARRY OUT TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . .. 150 PRE-DIAGNOSTIC QUESTIONING . . . . . . . . . . . .. 152 SYMPTOM CHART . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 54 ® CHECKING AND CLEARING DIAGNOSTIC CODES "CHECK ENGINE" LAMP CHECK . . . . . . . . . . . . . 159 OUTPUT OF DIAGNOSTIC CODES 1 . Normal mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 9 2. Test mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 CLEARING DIAGNOSTIC CODE . . . . . . . . . . . . . . . . 162 IS SYMPTOM SIMULATION . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 ® BASIC INSPECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167 INSPECTION AND ADJUSTMEN T GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 IDLE SPEED AND IDLE MIXTURE . . . . . . . . . . . .. 172 MANIFOLD PRESSURE SENSOR (VACUUM SENSOR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 THROTTLE POSITION SENSO R (LINEAR TYPE) AND THROTTL E BODY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 DISTRIBUTOR (G AND NE SIGNALS) . . . . . . . . 180 INTAKE AIR TEMPERATURE SENSOR . . . . . . . 181 FEEDBACK CORRECTION . . . . . . . . . . . . . . . . . . . . . . . 182 Models with oxygen senso r (02 sensor) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 182 Models with lean mixture sensor . . . . . . . . . .. 183 VARIABLE RESISTOR . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 184 ISC VALVE (DUTY-CONTROL ACV TYPE) . . . . . . . . . . . . . . 186 Page APPENDIX ENGINE CONTROL SYSTE M SPECFICATION CHART . . . . . . . . . . . . . . . . . . . . . . . . 188 DELETED FOR NEW EDITIO N . . . . . . . . . . . . . . . . . . . . 118, 119, 125, 126, 141 to 144, 166 and 174 ABBREVIATIONS AND ECU TERMINAL SYMBOLS - Abbreviations 4 ABBREVIATIONS AND ECU TERMINAL SYMBOLS ABBREVIATION S ABS Anti-Lock Brake System ABV Air Bypass Valv e AC Alternating Current A/C Air Conditione r ACIS Acoustic Control Induction System ACV Air Control Valv e Al Air Injection AS Air Suction ASV Air Switching Valve A/T Automatic Transmission BTDC Before Top Dead Center CA Crankshaft Angl e CALIF Californi a CCS Cruise Control System CO Carbon Monoxid e DIS Direct Ignition System DLI Distributorless Ignition EC European Countrie s ECT Electronically-Controlled Transmission ECU Electronic Control Unit EFI Electronic Fuel Injection EGR Exhaust Gas Recirculatio n EHPS Electro-Hydraulic Power Steering ESA Electronic Spark Advance FED. Federal GEN. General Countries HAC High-Altitude Compensation HC Hydrocarbo n HIC Hybrid Integrated Circui t IIA Integrated Ignition Assembly ISC Idle Speed Contro l LED Light Emitting Diode LS Lean Mixture Senso r MRE Magnetic Resistance Element M/T Manual Transmission NOx Oxides of Nitrogen OC Oxidation Catalyst OD Overdrive 02 Oxygen PS Power Steering SCV Swirl Control Valve SST Special Service Tool SW Switch TCCS Toyota Computer-Controlled System TDC Top Dead Cente r TDCL *1 Toyota Diagnostic Communication Link or Total Diagnostic Communication Lin k TEMS Toyota Electronically-Modulated Suspension Tr Transisto r TRC*2 Traction Contro l T-VIS Toyota-Variable Induction System TWC Three-Way Catalyst U.S. United States VSV Vacuum Switching Valve w/ Wit h w/o Without 4WD 4-Wheel-Driv e In vehicles sold at Lexus dealers in the U.S . and Canada, this is called the "Total Diagnostic Communication Link" . In Toyotas sold in other countries, and in Toyotas sold at Toyota dealers in the U.S . and Canada, it is called the "Toyota Diagnostic Communication Link" . In this manual, it is called the "Toyota Diagnostic Communication Link" . *2 In the U .S . and Canada, this is abbreviated to TRAC . /-- iw 1 c Abbreviations in accordance with SAE terms are used for vehicles sold in the U .S .A . and Canada. Refer to the Repair Manual for dif- ferences between SAE terms and Toyota terms . Example : ECM Engine Control Module (= Engine ECU ) ECT Engine Coolant Temperature (= THW) 1 ABBREVIATIONS AND ECU TERMINAL SYMBOLS - ECU Terminal Symbol s ECU TERMINAL SYMBOL S SYMBOL MEANING ABS Anti-Lock Brake Syste m ACC1 Acceleration Signal No . 1(from Thrott le Position Sensor) ACC2 Acceleration Signal No . 2 (from Throttle Position Sensor) A/C Air Conditione r ACMG Air Conditioner Magnetic Clutch ACT Air Conditioner Cut-Of f Al Air Injection AS Air Suctio n A/D Auto Drive (Cruise Control System) +B Battery +B1 Battery No. 1 BATT Batt e ry BF Batte ry Fail Safe BRK Brake DFG Defogge r E01 Ea rth No . 01 (Ground) E02 Earth No. 02 (Ground) E1 Ea rth No. 1 (Ground) E2 Ea rth No . 2 (Ground ) ECT Electronically-Controlled Transmission ELS Electrical Load Signa l EGR Exhaust Gas Recirculation FC Fuel Pump Contro l FP Fuel Pump Control Relay FPU Fuel Pressure-U p FS Fail-Safe Relay G Group (Crankshaft Angle Signal ) G1 Group No . 1 (Crankshaft Angle Signal) G2 Group No . 2 (Crankshaft Angle Signal) G- Group Minus (- ) HAC High-Altitude Compensatio n HT Heater (for Oxygen Sensor or Lean Mixture Sensor ) IDL Idle Switch (in Throttle Position Sensor ) IGDA Ignition Distribution Signal A IGDB Ignition Distribution Signal B IGF Ignition Failure (Confirmation) Signal IGSW Ignition Switc h IGT Ignition Timing Signal SYMBOL MEANIN G ISC1 Idle Speed Control Signal No . 1 ISC2 Idle Speed Control Signal No . 2 ISC3 Idle Speed Control Signal No . 3 ISC4 Idle Speed Control Signal No . 4 KD Kick-Dow n KNK Knock Sensor KS Karman Signa l L7 Throttle Valve Opening Signal No . 1 L2 Throttle Valve Opening Signal No . 2 L3 Throttle Valve Opening Signal No . 3 LP Lamp LS Lean Mixture Sensor LSW Lean Burn Switch M-REL EFI Main Rela y N/C Neutral Clutch Switch NE Number of Engine Revolutions Signa l NE- Number of Engine Revolutions Signal Minus (- ) NEO Number of Engine Revolutions Signal Outpu t No.10 (for Injectors) No.20 (for Injectors ) NSW Neutral Start Switch OX Oxygen Sensor OX + Oxygen Sensor ~+ OIL Oil Pressure OD Overdrive PS Power Steerin g PSW Power Switch (in Throttle Position Sensor ) PIM Pressure, Intake Manifol d R-P Regular or Premium Gasoline Signal RSC Rota ry Solenoid Valve Close d RSO Rota ry Solenoid Valve Open SCV Swirl Control Valv e SPD Vehicle Speed SP2 Vehicle Speed No . 2 SP2- Vehicle Speed No . 2 Minus (-) STA Sta rter STJ Cold Start Injecto r 2 ABBREVIATIONS AND ECU TERMINAL SYMBOLS - ECU Terminal Symbol s SYMBOL MEANING STP Stop Lamp Switch T Test Termina l TE1 Test Terminal, Engine No . 1 TE2 Test Terminal, Engine No . 2 THA Thermo, Intake Ai r THG Thermo, Exhaust Gas THW Thermo, Wate r TR Traction Contro l T-VIS Toyota-Variable Induction System TSW Water Temperature Switc h VAF Voltage, Air-Fuel Ratio Control VB Voltage, Battery VC Voltage, Constant VF Voltage, Feedbac k VG Voltage, Gram Intake Air V-ISC VSV Type Idle Speed Control VS Voltage, Slide Signa l VSH Voltage, Sub-Throttle Angle VTA Voltage, Throttle Angle VTH Voltage, Throttle Angl e W "CHECK ENGINE" Warning Lamp WIN Warning Lamp, Intercooler F4$ 3 b OW3W OUTLINE OF TCCS - What is TCCS ? OUTLINE OF TCCS WHAT IS TCCS ? "TCCS" (Toyota Computer-Controlled System) is the general name for a system which exercises comprehensive and highly precise control of the engine, drive train, brake system, and other systems by means of an ECU* (electronic control unit), at the heart of which is a microcomputer . Previously, TCCS was used as an engine control system for only EFI (electronic fuel injection), ESA (electronic spark advance), ISC (idle speed control), diagnosis, etc . Later, control systems utilizing other separate ECUs were developed and adopted for the control of systems other than the engine also . Currently, the term "TCCS" has come to mean a comprehensive control system which incorpo- ® rates control systems controlled by various ECUs to ensure basic vehicle performance, not only running, turning and stopping . *At Toyota, a computer which controls each type of system is called an "ECU" . REFERENCE On some vehicle models, the ECT has its own ECU, called the "ECT ECU" . (The ECU for engine control is called the "Engine ECU" in this case .) On models in which the ECT does not have its own separate ECU, the ECT uses the ECU for engine control, which is then called the "Engine and ECT ECU" . TCCS CONCEPTUAL DIAGRAM OF TCCS This manual explains the TCCS type engine control system . For details concerning other systems (ECT, ABS, TEMS, etc .), please refer to the training manual for each individual system . OHP 1 In addition, this manual assumes that you have mastered the contents of the manual for Step 2, vol . 5 (EFI) . If you have not, please read that manual carefully before beginning this one . 5 11 OUTLINE OF TCCS - History of TCCS Engine Control Syste m HISTORY OF TCCS ENGINE CONTROL SYSTE M The ECU used for conventional EFI in export models beginning in 1979 was the analog circuit type, which controlled the injection volume based on the time required for a capacitor to be charged and discharged . The microcomputer-controlled type was added beginning in 1981 . That was the beginning of the engine control system using TCCS . Now , however, the TCCS engine control system not only controls EFI, but also ESA, which controls ignition timing ; ISC, which controls the idle speed, and other such advanced systems; as well as the diagnostic, fail-safe, and back-up functions . CYL . ARR . ENGINE MODELS 1980 1985 1990 199 5 K series ( 4K-E) -- ~ E series ( 3E-E) [2E-E, 4E-FE, 5E-FE ] A series (4A-GE, 4AG-ZE ) [4A-FE, 5A-FE, 7A-FE ] L4 S series ( 2S-E ) (1 S-i, 1S-E, 2S-E) 1 3S-FE, 5S-FE , 3S-GE, 3S-GTE ] R series ( 22R-E ) (22R-TE) [22R-E] ~ Y series ( 3Y-E ) [4Y-E ] RZ series [1RZ-E, 2RZ-E, 2RZ-FE, 3RZ-FE 1 TZ series [2TZ-FE, 2TZ-FZE] ~ G series ( 1G-E)[1G-FE ] (1G-GE) -----~ ~ L6 M series (4M-E, 5M-E, 5M-GE ) (5M-GE, 6M-GE, 7M-GE, 7M-GTE ) JZ series [2JZ-GE, 2JZ-GTE] ~ F series (3F-E) ~ FZ series [ 1 FZ-FE ] V6 VZ series (2VZ-FE)[3VZ-E, 3VZ-FE, 5VZ-FE ] MZ series [1 MZ-FE ] V8 UZ series [1UZ-FE ] INTAKE AIR SENSING DEVICES Vane type air flow meter - Manifold pressure (vacuum) senso r Optical Karman vortex type air flow mete r Hot-wire type mass air flow meter - 1 : No longer in production models I I : Current product models ---~ : EFI (EFI control only ) TCCS (EFI, ESA, ISC, Diagnosis, etc ) 6 OUTLINE OF TCCS - System Description SYSTEM DESCRIPTIO N The functions of the engine control system In addition, there are auxiliary engine control include EFI, ESA, and ISC, which control basic devices on the engine, such as the OD cut-off con- engine performance ; a diagnostic function, trol system, intake air control system, and others . which is useful when repairs are made ; and fail- These functions are all controlled by the Engine safe and back-up functions, which operate when ECU . any of these control systems malfunction . Manifold pressure sensor Fuel pum p Knock sensor Distributor ,( and ignite r Water temp . sensor "E Ignition switc h Circuit opening relay Engine EC U Variable resistor ' Check connector Idle speed control valv e Intake air temp . senso r "Applicable only to General Country specification vehicles without oxygen sensor . LAYOUT OF ENGINE CONTROL SYSTEM COMPONENTS (COROLLA 4A-FE ENGINE FOR EUROPE Apr ., 1992) 7 0 OUTLINE OF TCCS - System Descriptio n 1 . FUNCTIONS OF ENGINE CONTROL SYSTE M EFI (ELECTRONIC FUEL INJECTION ) An electric fuel pump supplies sufficient fuel, under a constant pressure, to the injectors . These injectors inject a metered quantity of fuel into the intake manifold in accordance with signals from the Engine ECU . The Engine ECU receives signals from various sensors indicating changing engine operating conditions such as :  Manifold pressure (PIM) or intake air volume (VS, KS or VG )  Crankshaft angle (G)  Engine speed (NE )  Acceleration/deceleration (VTA)  Coolant temperature (THW )  Intake air temperature (THA) etc . ESA (ELECTRONIC SPARK ADVANCE ) The Engine ECU is programmed with data that will ensure optimal ignition timing under any and all operating conditions . Based on this data, and on data provided by the sensors that monitor various engine operating conditions, such as those shown below, the Engine ECU sends IGT (ignition timing) signals to the igniter to trigger the spark at precisely the right instant .  Crankshaft angle (G )  Engine speed (NE )  Manifold pressure ( PIM) or intake air volume (VS, KS or VG )  Coolant temperature (THW) etc . Igniter and ignition coi l These signals are utilized by the Engine ECU to determine the injection duration necessary for the optimal air-fuel ratio to suit the present engine running conditions . Fue l + Engine ECU Sensors OHP 3 Sensor s OHP 3 8 OUTLINE OF TCCS - System Description ISC (IDLE SPEED CONTROL ) The Engine ECU is programmed with target engine speed values to respond to different engine conditions such as :  Coolant temperature (THW)  Air conditioner on/off (A/C) etc . Sensors transmit signals to the Engine ECU, which, by means of the ISC valve, controls the flow of air through the throttle valve bypass and adjusts the idle speed to the target value . ISC valve DIAGNOSTIC FUNCTIO N The Engine ECU is constantly monitoring the signals that are input to it from the various sensors . If it detects any malfunctions in the input signals, the Engine ECU stores data on the malfunction in its memory and lights the "CHECK ENGINE" lamp . When necessary, it displays the malfunction by lighting the "CHECK ENGINE" lamp, displaying on a tester* or output- ting a voltage signal . * OBD-II scan tool or TOYOTA hand-held teste r "CHECK ENGINE" lamp OHP 4 Sensors OHP 4 FAIL-SAFE FUNCTIO N If the signals input to the Engine ECU are abnormal, the Engine ECU switches to standard values stored in its internal memory to control the engine. This makes it possible to control the engine so as to continue more-or-less normal vehicle operation . BACK-UP FUNCTIO N Even if the Engine ECU itself becomes partially inoperative, the back-up function can continue to execute fuel injection and ignition timing control . This makes it possible to control the engine so as to continue more-or-less normal vehicle operation . OTHER CONTROL SYSTEM S In some engines, the OD cut-off control system, intake air control system, and some other aux- iliary systems are also controlled by the Engine ECU . 9 ® OUTLINE OF TCCS - System Descriptio n 2. CONSTRUCTION OF ENGINE CONTROL SYSTE M BLOCK DIAGRAM The engine control system can be broadly The sensors and actuators which form the basis divided into three groups : the sensors, the of an engine control system used in an engine Engine ECU and the actuators . with an oxygen sensor are shown below . SENSORS MANIFOLD PRESSURE I I I I EF I SENSOR (D-TYPE EFI ) AIR FLOW METER*2 (L-TYPE EFI ) DISTRIBUTOR ----------------------------  Crankshaft angle signa l  Engine speed signa l WATER TEMP . SENSO R INTAKE AIR TEMP . SENSO R THROTTLE POSITION SENSO R  Idling signa l  Throttle position signa l IGNITION SWITCH (ST TERMINAL )  Starting signa l VEHICLE SPEED SENSO R OXYGEN SENSOR VARIABLE RESISTOR- 3 NEUTRAL START SWITC H TAILLIGHT & DEFOGGER RELAY S AIR CONDITIONE R KNOCK SENSO R CHECK CONNECTOR OXYGEN SENSOR HEATER CONTRO L OXYGEN SENSOR HEATE R FUEL PUMP CONTRO L CIRCUIT OPENING RELAY CHECK ENGINE LAMP (Diagnostic code display ) PIM ~10 VS, KS #20 or VG G NE THW THA ID L T A STA SPD OX VAF NSW ELS A/C KNK TE TE IGT IG F IS C RSC ENGINE IRSO I ECU HT FC W BATT I 1 +13 BATTERY I I EFI MAIN RELA Y * 1 * 2 *3 Actuators only related profoundly to the engine control are shown here . Although a D-type EFI is shown in the above figure and a L-type EFI sensor is also shown for reference . Applicable only to General Country specification vehicles without oxygen sensor . ACTUATORS* ' NO .1 AND 3 INJECTOR S NO .2 AND 4 INJECTOR S ESA IGNITE R i IGNITION COIL i DISTRIBUTO R t SPARK PLUG S IS C IDLE SPEED CONTROL VALV E COROLLA 4A-FE ENGINE FOR EUROPE (Apr., 1992) 10 OUTLINE OF TCCS - System Descriptio n COMPONENTS AND FUNCTION S The sensors, Engine ECU, and actuators, which are the basis of the engine control system, are shown in the following table, along with their relationship with the main functions of the engine control system, EFI, ESA and ISC . ® REFERENCE The signals used for each control may differ for some engines . COMPONENTS SIG- FUNCTIONS EFI ESA IS C NAL S Manifold pressure senso r ( vacuum sensor) ( D-type PIM Senses intake manifold pressure . EFI ) Air flow meter VS, KS Senses intake air volume . (L-type EFI) or V G G Senses crankshaft angle . Distributor NE Senses engine speed . Water temp . sensor THW Senses coolant temperature . Intake air temp . sensor THA Senses intake air temperature . Throttle position sensor IDL Senses when throttle valve is fully closed . (on-off type) PSW Senses when throttle valve near fully open . Throttle position sensor IDL Senses when throttle valve is fully closed . Sensors (linear type) VTA Senses throttle valve opening angle . Ignition switch STA Senses when ignition switch is start position . Vehicle speed sensor SPD Senses vehicle speed . Oxygen sensor OX Senses oxygen density in exhaust gas . (02 sensor) It is used to change the air-fuel ratio of the idl e Variable resistor VAF mixture . Senses whether transmission is in "P" or "N" , Neutral start switch NSW or in some other gear . Taillight & defogger relays ELS Senses electrical load . Air conditioner A/C Senses whether air conditioner is on or off . Knock sensor KNK Senses engine knocking . Determines injection duration and timing, igni - tion timing, idle speed, etc ., based upon dat a Engine ECU from sensors and data stored in memory, an d sends appropriate signals to control actuators . No .10 Injects fuel into intake manifold in accordanc e Injectors No .20 with signals from Engine ECU . When IGT signals from Engine ECU go off , IGT primary current to igniter is interrupted, an d Actuators Igniter IGF sparks are generated by spark plugs . Ignite r then sends IGF signals to Engine ECU . Controls idle speed by changing volume of ai r Idle speed control valve ISC flowing through throttle valve bypass in accor - dance with signals from Engine ECU . 11 a OUTLINE OF TCCS - System Description 3 . ENGINE CONTROL SYSTEM DIAGRAM Neutral start switch ~ ~ Check connecto r Pressure regulator / Injector Circuit opening relay Fuel pump Speed sensor J Combination meter Fuel tank Air conditioner amplifier i f Engine EC U Distributor and ignite r Knock sensor Variable resistor * Oxygen sensor (02 sensor) / r Water temp . sensor Battery TWC *Applicable only to General Country specification vehicles without oxygen sensor . COROLLA 4A-FE ENGINE FOR EUROPE (Apr ., 1992) Taillight relay Defogger relay r-o ~ Ignition switc h CHECK ~ ENGINE " ~ lam p 12 ELECTRONIC CONTROL SYSTEM - Genera l ELECTRONIC CONTROL SYSTE M GENERAL The engine control system can be divided into three groups: sensors (and the signals output by them), the ECU, and actuators . This section describes only the sensor (signal) systems . ECU functions are divided into EFI control, ESA control, ISC control, diagnostic function, fail-safe function, back-up function and others . Each of these functions is covered in a separate section of this manual . Actuator functions are also covered in a separate section . 411 The following table shows the specifications for the 4A-FE engine . Information on sensors (and their signals) marked with a circle in the "APPENDIX" column is included in the specifications for each engine in the APPENDIX section (page 188) at the back of this manual . Sensors (signals) covered in Step 2, vol . 5 (EFI), are covered in outline form only in this manual . If there is a circle in the "STEP 2(EFI)" column in the following table, refer to the Step 2, vol . 5 (EFI), for a detailed explanation of the relevant sensors (and their signals) . SENSORS (SIGNALS) PAG E (THI S MANUAL) ITEM REMARK APPENDIX STEP 2 (EFI ) Engine without steppe r motor type ISC valve 15 0 Power circuitry Engine with steppe r motor type ISC valve 1 6 VC circuitry 16 0 Ground circuitry 16 0 Manifold pressure senso r (vacuum sensor) 17 0 Vane type 1 8 Air flow meter Optcal Karman vorte x type 2 1 Hot-wire type 21- 1 Throttle On-off type 22 position sensor Linear type 23 0 In-distributor type 24 G and NE signa l enerators Cam position sensor type 27 g Separate type 28 Water temperature sensor 30 Intake air temperature sensor 30 Oxygen sensor Zirconia element type 31 With TW C (02 sensor) Titania element type 3 2 Lean mixture sensor 3 3 ` Specifications for Carolla AE101 4A-FE engine (Apr ., 1992) (Continued on next page ) 13 ELECTRONIC CONTROL SYSTEM - Genera l SENSORS (SIGNALS) PAG E (THIS ITEM* REMARK APPENDIX STEP 2 MANUAL) (EFI ) Reed switch type 34 Photocoupler type 34 Vehicle speed Electromagnetic pickup 3 5 sensor type MRE (magnetic resistance 36 ~ element) typ e STA (ignition switch) signal 38 J ~ NSW (neutral start switch 1 signal 38 A/C (air conditioner) signal 39 0 Electrical load signal 39 0 Fuel control switch or connector 40 EGR gas temperature sensor 40 r~ Californi a specification model s Variable resistor 41 C Except with oxyge n senso r Kick-down switch 42 Water temperature switch 42 Clutch switch 42 Knock sensor 43 With knocking correction for ES A HAC (high-altitude compensation) sensor 44 Turbocharging pressure sensor 44 Stop lamp switch 45 Oil pressure switch 4 5 Throttle opening angle 45 signal s Throttle opening angl e signals for TRC (traction 4 5 control) syste m Cruise control system 4 6 communications signa l TRC system 4 6 Communications communications signa l signals ABS (anti-lock brak e system) communications 4 6 signa l Intercooler system 4 6 warning signa l EHPS lelectro-hydrauli c power steering) system 4 7 communications signa l Engine speed signal 4 7 Diagnostic terminal (s) 4 7  Specifications for Corolla AE101 4A-FE engine (Apr ., 1992 ) 14 ELECTRONIC CONTROL SYSTEM - Power Circuitry POWER CIRCUITRY This circuitry supplies power to the Engine ECU, and includes the ignition switch and the EFI main relay. There are two types of this circuitry in use. In one, current flows directly from the ignition switch to the EFI main relay coil to operate the EFI main relay (the type without the stepper motor type ISC valve) . In the other, the Engine ECU operates the EFI main relay directly ELECTRICAL CIRCUITR Y EFI fuse (the type with the stepper motor type ISC Battery valve) . 1 . ENGINE WITHOUT STEPPER MOTOR TYPE ISC VALV E The following diagrams show the type in which the EFI main relay is operated directly from the ignition switch. When the ignition switch is turned on, current flows to the coil of the EFI main relay, causing the contacts to close . This supplies power to the +B and +B1 terminals of the Engine ECU . Battery voltage is supplied at all times to the BATT terminal of the Engine ECU to prevent the diagnostic codes and other data in its memory from being erased when the ignition switch is turned off . There are two types of circuitry for the type without a stepper motor, depending on the vehicle model . To stop lamp switc h STOP fuse Battery * Some models only ® Engine EC U BATT OHP 7 Engine EC U OHP 7 15 ELECTRONIC CONTROL SYSTEM - Power Circuitry, VC Circuitry, Ground Circuitry 2 . ENGINE WITH STEPPER MOTOR TYPE ISC VALV E The diagram below shows the type in which the EFI main relay is operated from the Engine ECU . In engines with the stepper motor type ISC valve, since initial set control is carried out when the ignition switch is turned off, power is supplied to the Engine ECU for this purpose for approximately 2 seconds after the ignition switch is turned off . (For further details, see page 105.) When the ignition switch is turned on, battery voltage is supplied to the IGSW terminal of the Engine ECU, and the EFI main relay control circuitry in the Engine ECU sends a signal to the M-REL terminal of the Engine ECU, turning on the EFI main relay . This signal causes current to flow to the coil, closing the contacts of the EFI main relay and supplying power to the +B and +B1 terminals of the Engine ECU . Battery voltage is supplied at all times to the BATT terminal of the Engine ECU to prevent the diagnostic codes and other data in its memory from being erased when the ignition switch is turned off . ELECTRICAL CIRCUITR Y EFI fus e Battery Engine ECU ELECTRICAL CIRCUITRY Engine ECU Some models only OHP 8 1 Outputs 5 V from the 5-V constant-voltage circuit . 2 Outputs 5 V from the 5-V constant-voltag e circuit through a resistor . ~ NOT E When the VC circuit is open or shorted, each of the sensors using the 5 V constant voltage of the VC is no longer activated . In addition, since the microprocessor will no longer be activated when the VC circuit is shorted, the engine ECU will not operate . As a result, the engine will stall . GROUND CIRCUITRY The Engine ECU has the following three types of basic ground circuitry :  El terminal, which grounds the Engine ECU .  E2 terminal, which grounds the sensors .  E01 and E02 terminals, which ground the drive circuits for the injectors or ISC valve, etc . These ground circuits are connected inside the Engine ECU as shown in the following diagram . ELECTRICAL CIRCUITRY VC CIRCUITRY Some models only OHP 7 Engine ECU /I - E2 The Engine ECU generates a constant 5 volts to power the microprocessor from the battery voltages supplied to the +B and +B1 terminals . The Engine ECU supplies this 5 V of power to the sensors through circuitry like that shown below . To sensors . El To ground E01 OHP 8 E02 16 ELECTRONIC CONTROL SYSTEM - Manifold Pressure Sensor (Vacuum Sensor ) MANIFOLD PRESSURE SENSOR (VACUUM SENSOR ) The manifold pressure sensor is used with D- type EFI for sensing the intake manifold pressure . This is one of the most important sensors in D- type EFI . By means of an IC built into this sensor, the manifold pressure sensor senses the intake manifold pressure as a PIM signal . The Engine ECU then determines the basic injection duration and basic ignition advance angle on the basis of this PIM signal . Intake manifold pressure OHP 9 A change in the intake manifold pressure causes the shape of the silicon chip to change, and the resistance value of the chip fluctuates in accordance with the degree of deformation . This fluctuation in the resistance value is converted to a voltage signal by the IC built into the sensor and is then sent to the Engine ECU from the PIM terminal as an intake manifold pressure signal . The VC terminal of the Engine ECU supplies a constant 5 volts as a power source for the IC . (V) 4 ~ rn 3 OHP 9 f Intake manifold pressure OPERATION AND FUNCTION OHP 9 A silicon chip combined with a vacuum chamber maintained at a predetermined vacuum is incorporated into the sensor unit . One side of the chip is exposed to intake manifold pressure and the other side is exposed to the internal vacuum chamber . Engine EC U 0 20 60 100 kPa (abs) (760, 29.9) (610, 24 .0) (310, 1 2 .2) (10, 0 .4) (mmHg , in .Hg Intake manifold pressure [vacuum] ) ELECTRICAL CIRCUITR Y Manifold pressure sensor 1 5 V R IC VC PI M E2 E l To intake manifold Silicon chip / OHP 10 17 ® NOTE ELECTRONIC CONTROL SYSTEM - Manifold Pressure Sensor (Vacuum Sensor), Air Flow Mete r The manifold pressure sensor uses the vacuum in the vacuum chamber that is built into it. The vacuum in this chamber is close to a perfect vacuum, and is not influenced by the changes in atmospheric pressure that occur due to changes in altitude . The manifold pressure sensor compares the intake manifold pressure to this vacuum, and outputs a PIM signal which is not influenced by changes in atmospheric pressure . This permits the ECU to keep the air-fuel ratio at the optimal level even at high altitudes . AIR FLOW METE R The air flow meter is used with L-type EFI for sensing the intake air volume . In L-type EFI, this is one of the most important sensors. The intake air volume signal is used t o calculate the basic injection duration ignition advance angle . The following three types of air flow used : Vane type Volume air flow -F meter and basic meter are L Optical Karman vortex typ e Mass air flow _ Hot-wire type mete r Perfect Atmospheri c vacuum pressur e p 101.3 200 kPa (0, 0) (760, 29.9) (1500, 59 .1) (mmHg, . . . . . . . . . in.Hg) Absolute pressur e 101 .3 (760, 29.9 ) Vacuum 0 (0, 0 ) Vacuum 0 (0, 0 ) (sea level ) (high altitude) OHP 10 1 . VANE TYP E There are two types of vane type air flow meter . These differ in the nature of their electrical circuitry, but the components for the two types are the same . This type of air flow meter is composed of many components, as shown in the following illustration : Potentiomete r Slide r Return spring Idle mixture adjusting screw Bypass passage Measuring plate OHP 1 1 18 ELECTRONIC CONTROL SYSTEM - Air Flow Meter OPERATION AND FUNCTIO N When air passes through the air flow meter from the air cleaner, it pushes open the measuring plate until the force acting on the measuring plate is in equilibrium with the return spring . The potentiometer, which is connected coaxially with the measuring plate, converts the intake air volume to a voltage signal (VS signal) which is sent to the Engine ECU . The damping chamber and compensation plate act to prevent the measuring plate from vibrating when the air intake volume changes suddenly . Potentiometer OHP 1 1 IDLE MIXTURE ADJUSTING SCRE W An idle mixture adjusting screw is included in the bypass passage . This screw is used to adjust the volume of intake air which bypasses the measuring plate, and can be used to adjust the idle mixture. (Some engines are equipped with air flow meters which are sealed with an aluminum plug .) ® REFERENCE Standard Adjustment Mark of Idle Mixture Adjusting Scre w As shown in the illustration, a two digit number is stamped on the air flow meter near the idle mixture adjusting screw. This number indicates the distance from the body upper surface to the flat surface of the screw when the VS voltage of the air flow meter is at the standard voltage at the time that the volume of air through the bypass was adjusted during final inspection of the air flow meter at the factory. For example, if the number is "30", it means that the distance was 13.0 mm (0 .511 in) . If the number is "26", it indicates the distance was 12 .6 mm (0 .496 in) . Air flow meter Idle mixture adjusting scre w Idle mixture adjusting screw 19 ® VS SIGNAL ELECTRONIC CONTROL SYSTEM - Air Flow Mete r There are two types of vane type air flow meter, which differ in the nature of their electrical circuitry. In one type, the VS voltage falls when the air intake volume becomes large and in the other type, the VS voltage rises when the air intake volume becomes large . 1 Type 1 The Engine ECU has a built-in constant-voltage circuit, which supplies a constant 5 V to the VC terminal of the air flow meter. Consequently, the output voltage at the VS terminal will always indicate the exact opening angle of the measuring plate, and therefore, the exact intake air volume . Fuel pump switch Potentiometer FC E1 E2 VC E2 (E1) (FC) ~a~n~a~ff ;o-ts a v VS OHP 12 f2 ) Type 2 This type of air flow meter is supplied with ba ttery voltage from the VB terminal . This type of air flow meter does not have a constant voltage (5 V) supplied from the Engine ECU, so the voltage determined by the ratio of the resistances of the resistor between VB and VC and the resistor between VC and E2 is input to the Engine ECU via the VC terminal . As a result, even when the VS voltage is affected by fluctuations in the battery voltage, the Engine ECU, by executing the following calculation, can detect the intake air volume accurately : Intake air volume = VB - E2 VB - E2 (VC - E2) - (VS - E2) VC - VS For fu rther details, see Step 2, vol . 5 (EFI) . Fuel pump switch Potentiomete r Voltage of battery THA A VC " E 2 5.0-i Voltage (V) VC H E2 VS H E2 0 1 Measuring plate opening angle (intake air volume) OHP 1 2 20 Voltage (V) OHP 1 2 VBHE 2 VS H E2 0 Measuring plate opening angl e (intake air volume) OHP 12 ELECTRONIC CONTROL SYSTEM - Air Flow Meter 2 . OPTICAL KARMAN VORTEX TYP E This type of air flow meter directly senses the intake air volume optically. Compared to the vane type air flow meter, it can be made smaller and lighter in weight . The simplified construction of the air passage also reduces inlet resistance . This air flow meter is constructed as shown in the following illustration : Mirror LED Leaf sprin g From W~'M I To air air moo, Karman ♦ intake creaner ~9 vn.toYO~ chambe r Pressure- directin Mirro r ~ Pressure ~ directing aperture OHP 1 3 Vortex / ___ . . 9 Phntntrancictn r generator OHP 1 3 OPERATION AND FUNCTIO N A pillar (called the "vo rtex generator") placed in the middle of a uniform flow of air generates a vortex called a "Karman vo rtex" down-stream of the pillar . The frequency "f" of the Karman vortex thus generated, the velocity of the air "V" and the diameter of the pillar "d" have the following relationship : f - K x d ® of a piece of thin metal foil (called a "mirror") to the pressure of the vortexes and optically detecting the vibrations of the mirror by means of a photocoupler (an LED combined with a phototransistor) . LED r=^ Phototransisto r Vortex - generato r The intake air volume (KS) signal is a pulse signal like that shown below . When the intake air volume is low, this signal has a low frequency. When the intake air volume is high, this signal has a high frequency . High Voltage signa l Low Low Intake air volume Hig h OHP 1 3 ELECTRICAL CIRCUITR Y Air flow meter Pillar (vo rtex generator ) KARMAN VORTEX OHP 1 3 Utilizing this principle, the frequency of the vortexes generated by the vortex generator is measured, making it possible to determine the air flow volume . Vortexes are detected by subjecting the su rface Phototransistor Engine EC U OHP 13 21 4 3 . HOT-WIRE TYPE ELECTRONIC CONTROL SYSTEM - Air Flow Meter Instead of measuring intake air volume in the man- ner of other air flow meters, a hot-wire type air flow meter measures intake air mass directly . The structure is both compact and lightweight . In addition, there is only a low level of intake resistance by the sensor . Having no mechanical functions it offers a superior durability . Thermisto r F ~ REFERENC E A hot-wire type air flow meter as shown below is used on some models . OPERATION AND FUNCTIO N Current flows to the hot-wire (heater) causing it to be heated . When air flows through the wire, the hot-wire is cooled corresponding to the intake air mass . By controlling the current flowing to the hot-wire in order to keep the hot-wire temperature constant, that current becomes proportional to in- take air mass. Intake air mass can then be measured by detecting that current . In case of hot-wire type air flow meters, this current is con- verted into a voltage that is then output to the Engine ECU . Hot-wire (heater) * *Constant temperatur e Thermistor Intake air mass --- (g/sec .) ELECTRONIC CONTROL SYSTEM - Air Flow Mete r In an actual air flow meter, a hot-wire is incor- porated into the bridge circuit . This bridge circuit has the characteristic of the potentials at points A and B being equal when the product of resistance along the diagonal line is equal ([Ra + R3]  R1 = Rh  R2) . When the hot-wire (Rh) is cooled by in- take air, resistance decreases resulting in the for- mation of a difference between the potentials of points A and B . An operational amplifier detects this difference and causes a rise in the voltage ap- plied to the circuit (increases the current flowing to the hot-wire (Rh)) . When this is done, the temperature of the hot-wire (Rh) again rises resulting in a corresponding increase in resistance until the potentials of points A and B become equal (the voltages of points A and B become higher) . By utilizing the properties of this type of bridge circuit, the air flow meter is able to measure intake air mass by detecting the voltage at point B . Moreover, in this system, the temperature of the hot-wire (Rh) is continuously maintained at a constant temperature higher than the temperature of the intake air by using the ther- mistor (Ra) . Consequently, since intake air mass can be measured accurately even if intake air temperature changes, it is not necessary for the Engine ECU to correct the fuel injection duration for the intake air temperature . In addition, when air density decreases at high altitudes, the cooling capacity of the air decreases in comparison with the same intake air volume at sea level . As a result, the amount of cooling of the hot-wire is reduced . Since the intake air mass detected will also decrease the high-altitude compensation cor- rection is not necessary . ® Diagram Indicating Principle of Electrical Circuitry Air flow meter Engine EC U REFERENCE The voltage (V) required to raise the temperature of the hot-wire (Rh) by the amount of AT from the intake air temperature remains constant at all times even if the intake air temperature changes . In addition, the coolin g capacity of the air is always proportional to the intake air mass . Consequently, if the intake air mass remains the same, the output of the air flow meter will not change even if there is a change in intake air temperature . Hot-wire (Rh) temperature 20°C+ AT -- 0°C+OT -- 20°C 0°C v Intake air temperatur e NOTE An intake air temperature sensor is not required for the measurement of intake air mass due to the properties of a hot-wire type air flow meter . However, since intake air temperature is re- quired for other electronic control systems of the engine, the hot-wire type air flow meter has the built-in intake air temperature sensor . ELECTRONIC CONTROL SYSTEM - Throttle Position Senso r THROTTLE POSITION SENSO R The throttle position sensor is mounted on the throttle body . This sensor converts the throttle opening angle to a voltage and sends it to the Engine ECU as the throttle opening angle signal . The IDL signal is used mainly in fuel cut-off control and ignition timing corrections and the VTA or PSW signal is used mainly for increasing the fuel injection volume to increase engine output . There are two types of throttle position sensor, as follows :  On-off type  Linear typ e 1 . ON-OFF TYP E This type of throttle position sensor detects whether the engine is idling or running under a heavy load by means of the idle (IDL) contact or power (PSW) contact . Other terminals or contacts can also be used to perform other functions, depending on the type of engine. These include: the lean burn switch (LSW) contact, for lean burn correction; the L1, L2, and L3 terminals for control of the ECT ; the ACC1 and ACC2 terminals for sensing acceleration ; etc. For further details, see Step 2, vol. 5 (EFI) . 1 2-contact type 2 3-contact type 3 With L1, L2 and L3 terminal s IDL 4 With ACC1 and ACC2 terminal s ACC2 ELECTRICAL CIRCUITRY (2-CONTACT TYPE ) PSW ~ E IDL IDL H E On Of f PSW H E ' Off ~ On i I Throttle valve ---) Open OHP 14 OHP 1 4 22 ELECTRONIC CONTROL SYSTEM - Throttle Position Senso r 2 . LINEAR TYPE This sensor is composed of two sliders (at the tips of which are mounted the contacts for the IDL and VTA signals, respectively) . A constant 5 V is applied to the VC terminal from the Engine ECU . As the contact slides along the resistor in accordance with the throttle valve opening angle, a voltage is applied to the VTA terminal in proportion to this angle . When the throttle valve is closed completely, the contact for the IDL signal connects the IDL and E2 terminals . The VTA and IDL output signals are as shown in the table below . Slider ( contact for VTA signal) OHP 1 5 (V) 5-12fi } Idling Closed ~- Thrott le valve --~ Open OHP 15 ELECTRICAL CIRCUITRY OHP 1 5 *Depending on the model, this circuitry may include both resistors Ri and R2, Ri only, or R2 only . NOT E Recent linear type throttle position sensors in- clude models without an IDL point and the model with an IDL point but its terminal is not connected to the Engine ECU . In these models, the Engine ECU detects idling condition perfor- ming learned control by using the VTA signal . 23 0 ELECTRONIC CONTROL SYSTEM - G and NE Signal Generator s G AND NE SIGNAL GENERATOR S The G and NE signals are generated by the timing rotors or signal plates and the pickup coils. These signals are used by the Engine ECU to detect the crankshaft angle and engine speed . These signals are very important not only for the EFI system but also for the ESA system . The sensors which generate these signals can be divided into the following three types depending on their installation position, but their basic construction and operation are the same :  In-distributor typ e  Cam position sensor type  Separate type 1 . IN-DISTRIBUTOR TYP E The conventional governor advance and vacuum advance mechanisms have been eliminated in the distributor used with the TCCS engine control system, since spark advance is controlled electronically by the Engine ECU . The distributor in the engine control system contains the timing rotors and pickup coils for the G and NE signals . The number of teeth on the rotor and the number of pickup coils differ depending on the engine. Below, we will explain the construction and operation of the G and NE signal generators that use a single pickup coil and a 4-tooth rotor for the G signal, and a single pickup coil and 24- tooth rotor for the NE signal . G SIGNA L The G signal informs the Engine ECU of the standard crankshaft angle, which is used to determine the injection timing and ignition timing in relation to the TDC (top dead center) of each cylinder . The components of the distributor used to generate these signals are as follows : 1) The G signal timing rotor, which is fixed to the distributor shaft and turns once for every two rotations of the crankshaft . 2) The G pickup coil, which is mounted on the inside of the distributor housing . The G signal timing rotor is provided with four teeth which activate the G pickup coil four times per each revolution of the distributor shaft, generating the waveforms shown in the chart shown below . From these signals, the Engine ECU detects when each piston is near TDC (ex- ample : BTDC10°CA*) . " Depending on engine models . 1 turn of timing roto r 1800 CA (crankshaft angle ) G signal OHP 1 6 24 ELECTRONIC CONTROL SYSTEM - G and NE Signal Generator s NE SIGNA L The NE signal is used by the Engine ECU to detect the engine speed . NE signals are generated in the pickup coil by the timing rotor in the same way as with the G signal . The only difference is that the timing rotor for the NE signal has 24 teeth . It activates the NE pickup coil 24 times per each revolution of the distributor shaft, generating the waveforms shown in the chart . From these signals, the Engine ECU detects the engine speed as well as each 30° change in the engine crankshaft angle . NE signal timing rotor OHP 1 6 NE signal 1/2 turn of timing rotor ELECTRICAL CIRCUITRY, AND G AND NE SIGNAL WAVEFORMS 1 G signal (1 pickup coil, 4 teeth) NE signal ( 1 pickup coil, 24 teeth ) Engine EC U NE signal OHP 17 1800 CA OHP 1 7 (2) G signal ( 1 pickup coil, 2 teeth) NE signal (1 pickup coil, 24 teeth ) Engine ECU OHP 1 7 U U rrur 1 r 30° CA rrr OHP 16 G signa l NE signal 180° CA OHP 17 25 ELECTRONIC CONTROL SYSTEM - G and NE Signal Generator s 3 G1 and G2 signals (2 pickup coils, 1 tooth) 5 G signal (1 pickup coil, 1 tooth ) NE signal (1 pickup coil, 24 teeth ) Engine EC U OHP 1 8 F G1 signal '~ G2 signal 720° CA I NE signal (1 pickup coil, 4 teeth ) Engine ECU OHP 1 9 G signa l NE signa l NE signal IVU U U 180° CA OHP 18 4 NE signal (1 pickup coil, 4 teeth ) Engine ECU M1 Igniter a -1\ OHP 18 NE signal 180° CA OHP 18 180 0 6~ NE signal (2 pickup coils, 4 teeth ) Engine EC U NE signal 180° CA ~ 720° CA OHP 1 9 OHP 1 9 OHP 1 9 This type of circuit has two NE pickup coils connected in series . This is for the purpose of preventing noise in the NE signal during operation of the ignition coil . 26 ELECTRONIC CONTROL SYSTEM - G and NE Signal Generator s 7 G signal (1 pickup coil, 1 tooth) NE signal (2 pickup coils, 4 teeth ) Engine ECU 2 . CAM POSITION SENSOR TYP E The construction and operation of the cam posi- tion sensor is the same as for the in-distributor type, except for the elimination of the voltage distribution system from the distributor . G pickup coil G signal timing rotor NE signal--' 7200 CA ~. yi 1800 CA j OHP 2 0 OHP 2 0 This circuit also has two NE pickup coils for the same purpose as the circuit in © on the previous page . ~-- NOT E Depending on the engine model, there are also some Engine ECUs in which the G- terminal is grounded through a diode . When the diode is included in the circuit, a reading of approximately 0.7 V is obtained when measuring the voltage between G- an d El . Engine ECU OHP 20 NE signal timing rotor NE pickup coil OHP 2 1 ELECTRICAL CIRCUITRY, AND G AND NE SIGNAL WAVEFORM S G1 and G2 signals (2 pickup coils, 1 tooth) NE signal (1 pickup coil, 24 teeth ) Engine ECU Gl f Lml- G1 signa l G2 signal - NE signal 11--.1 1800 CA G2 NE I OHP 2 1 720° CA V OHP 21 27 a ELECTRONIC CONTROL SYSTEM - G and NE Signal Generator s 3 . SEPARATE TYPE Compared to the other types, the separate type G and NE signal generator differs in the sensor installation position, as shown in the following illustration . However, the basic function is the same . G pickup coil (G2) G pickup coil (G1 ) NE pickup coil OHP 2 2 Rotation of the G signal plate on the camshaft and the NE signal plate on the crankshaft alters the air gap between the projection(s) of the plate and the G pickup coil and the NE pickup coil. The change in the gap generates an electromotive force in the pickup coil . This creates the G and NE signals . L I IIIIIII Illr .,d,l,„J L~ _ I G PICKUP COI L NE PICKUP COIL G SIGNAL The G1 signal informs the Engine ECU of the standard crankshaft angle, which is used to determine the injection timing and ignition timing in relation to compression TDC of cylinder No. 6. The G2 signal conveys the same information for cylinder No . 1 . The sensors that generate these signals consist of a signal plate, which is fixed to the camshaft timing pulley and turns once per every two rotations of the crankshaft; and a pickup coil for the G signal, which is fitted to the distributor housing . The G signal plate is provided with a projection which activates the G pickup coil once per each rotation of the camshaft, generating waveforms like those shown in the following chart . From these signals, the Engine ECU detects when the No. 6 and No . 1 pistons are near their compression TDC . Camshaft timin g pulley G1 signa l G2 signal A G pickup coi l 3600 CA N No . 1 cylinder near TDC compression Camshaf t OHP 2 2 No . 6 cylinder near TDC compressio n OHP 2 2 No . 6 cylinder near TDC compressio n 28 ELECTRONIC CONTROL SYSTEM - G and NE Signal Generators NE SIGNAL F* 1 ELECTRICAL CIRCUITRY, AND G AND NE SIGNAL WAVEFORMS The NE signal is used by the Engine ECU to detect the engine speed . The Engine EC U determines the basic injection duration and basic G1 signal (1 pickup coil, 1 tooth) ignition advance angle by these signals . NE G2 signal (1 pickup coil, 1 tooth) signals are generated in the NE pickup coil by NE signal ( 1 pickup coil, 12 teeth ) the NE signal plate like the G signals . The only difference is that the signal plate for the NE signal has 12 teeth instead of just one . Therefore, 12 NE signals are generated per each engine revolution . From these signals, the Engine ECU detects the engine speed as well as each 30° change in the crankshaft angle . Engine ECU OHP 23 NE pickup coil rfimmimlii~ OHP 2 2 One rotation of NE signal plat e NE signal h I 1 ~r~rrur~ r i ~► - 30° CA irr OHP 22 F G1 signa l G2 signa l NE signal 1800 CA 7200 CA J OHP 23 29 ❑ ELECTRONIC CONTROL SYSTEM - G and NE Signal Generator s © G signal (1 pickup coil, 1 tooth ) NE signal (1 pickup coil, 36 minus 2 teeth ) Engine ECU e~N (NE This type of NE signal is able to detect both engine speed and crankshaft angle at the portion of two teeth missing . It is unable, however, to distinguish between the TDC of the compression stroke and that of the exhaust stroke . The G signal is used for this purpose . ,,-- REFERENC E 4A-FE engine which applies the Engine ECU made by Bosch uses G signal generator of the hall element type . Holl element will generate electromotive force in proportion to the changes of the magnetic flux . I G signa l NE signal YYVV W Y 720°CA 360°CA V _I L --I L 10°CA 30°CA 7 VVVYYVYYVVYVVY YtlYYVVVYYVYYYVVVYVYYYVYVYVYtlYYYY YVVVVYtlVVYVVY / NOTE The G signal timing rotor of the above described type in Z) is integrated into a single unit with the cam- shaft, while the NE signal timing rotor is integrated into a single unit with the crankshaft timing pulley . Also, the G signal generator is located in the distributor depending on the engine models . Camshaft A~B R A A ~ a 0 ~ I G pickup coi l Cylinder head NE signal timing rotor ELECTRONIC CONTROL SYSTEM - Water Temperature Sensor, Intake Air Temperature Sensor ® WATER TEMPERATURE INTAKE AIR TEMPERATURE SENSOR SENSO R This sensor detects the coolant temperature by This sensor detects the temperature of the means of an internal thermistor . intake air by means of an internal thermistor . ~ Thermistor OHP 24 ,4) For L-type EF I (vane type ) -20 0 20 40 60 80 100 120 (-4) (32) (68)(104)(140)(176)(212) (248) Temperature °C (°F) OHP 2 4 ELECTRICAL CIRCUITRY Engine ECU Thermisto r (1) For D-type EF I (optical Karman vortex type ) Air flow mete r Water temperature sensor (intake air temperature sensor) OHP 24 OHP 2 5 Intake air temp. sensor OHP 25 30 ® (hot-wire type) Intake Air Temperature Sensor, ELECTRONIC CONTROL SYSTEM - Oxygen Sensor (Oz Sensor ) ELECTRICAL CIRCUITR Y The electrical circuitry of the intake air temperature sensor is basically the same as that of the water temperature sensor. See the diagram for the electrical circuitry of the water temperature sensor . OXYGEN SENSOR (02 SENSOR ) In order for engines equipped with the TWC (three-way catalytic converter) to achieve the best purification performance, it is necessary for the air-fuel ratio to be kept within a narrow range near the theoretical (stoichiometric) air- fuel ratio . The oxygen sensor senses whether the air-fuel ratio is richer or leaner than the theoretical air- fuel ratio. It is located in the exhaust manifold, in the front exhaust pipe, etc . (This differs depending on the engine model . ) The following types of oxygen sensor are used ; they differ mainly in the material used for the element :  Zirconia element type  Titania element typ e 1 . ZIRCONIA ELEMENT TYP E This oxygen sensor consists of a element made of zirconium dioxide (Zr02, a kind of ceramic) . This element is coated on both the inside and outside with a thin layer of platinum. Ambient air is introduced into the inside of the sensor, and the outside of the sensor is exposed to exhaust gases . I Flang e = Platinum L- Zirconia element Platinu m Protective cover ELECTRONIC CONTROL SYSTEM - Oxygen Sensor (02 Sensor ) OPERATION If the oxygen concentration on the inside surface of the zirconia element differs greatly from that on the outside surface at high temperatures (400°C [752°F] or higher), the zirconia element generates a voltage, which acts as an OX signal to the Engine ECU, keeping it informed at all times about the concentration of oxygen in the exhaust gas . When the air-fuel mixture is lean, there is a lot of oxygen in the exhaust gas, so there is little difference between the oxygen concentration inside and outside the sensor element . For this reason, the voltage generated by the zirconia element is low (close to 0 V) . Conversely, if the air-fuel mixture is rich, the oxygen in the exhaust gas almost disappears . This creates a large difference in the oxygen concentrations inside and outside the sensor, so the voltage generated by the zirconia element is compara- tively large (approximately 1 V) . Theoretical air-fuel ratio ® ,,-- NOT E Even if the oxygen sensor is normal, if the out- side of the oxygen sensor is contaminated with mud, etc ., it could prevent outside air from get- ting into the oxygen sensor . The difference bet- ween the oxygen concentrations in the outside air and the exhaust gas will fall, so the oxygen sensor will always be sending a lean signal to the ECU . ELECTRICAL CIRCUITRY Engine ECU Oxygen sensor OHP 2 6 > m M No air Much air o into int o > exhaustga exhaustgas .. . D CL O i\ 0 Richer Air-fuel Leaner OHP 26 (no air) ratio (much air ) The platinum (with which the element is coated) operates as a catalyst, causing the oxygen and the CO (carbon monoxide) in the exhaust gas to react with each other. This decreases the oxygen volume and increases the sensitivity of the sensor . Based on the signal output by this sensor, the Engine ECU increases or reduces the injection volume to keep the air-fuel ratio at a constant value near the theoretical air-fuel ratio . Some zirconia oxygen sensors are provided with a heater which heats the zirconia element. The heater is also controlled by the ECU . When the intake air volume is low (that is, when the temperature of the exhaust gas is low), current flows to the heater to heat the sensor . For further details, see page 114 . 31 ELECTRONIC CONTROL SYSTEM - Oxygen Sensor (02 Sensor ) 2. TITANIA ELEMENT TYP E This oxygen sensor consists of a semiconductor element made of titanium dioxide (Ti02, which is, like Zr02, a kind of ceramic). This sensor uses a thick film type titania element formed on the front end of a laminated substrate to detect the oxygen concentration in the exhaust gas . Protective cover OHP 2 7 OPERATION The properties of titania are such that its resistance changes in accordance with the oxygen concentration of the exhaust gas . This resistance changes abruptly at the boundary between a lean and a rich theoretical air-fuel ratio, as shown in the following graph . The resistance of titania also changes greatly in response to changes in temperature. A heater is therefore built into the laminated substrate to keep the temperature of the element constant . x T Theoretical 8i air-fuel rati o ~ U V No air into exhaust gass Much air int o exhaustgass Richer a Air-fuel c* Leaner (no air) ratio ( much air) OHP 27 This sensor is connected to the Engine ECU, as shown in the following circuit diagram. A 1V potential is supplied at all times to the OX ±i terminal by the Engine ECU . The Engine ECU has a built-in comparator* which compares the voltage drop at the OX terminal (due to the change in resistance of the titania) to a reference voltage (0.45 V). If the result shows that the OX voltage is greater than 0 .45 V (that is, if the oxygen sensor resistance is low), the Engine ECU judges that the air-fuel ratio is rich . If the OX voltage is lower than 0 .45 V (oxygen sensor resistance high), it judges that the air- fuel ratio is lean . *See page 37 for details on the comparator . ELECTRICAL CIRCUITRY Engine ECU Check connector OX~ + OX OHP 2 7 1 V 0.45 V 32 ELECTRONIC CONTROL SYSTEM - Lean Mixture Senso r LEAN MIXTURE SENSO R The lean mixture sensor is constructed in basically the same way as the zirconia element type oxygen sensor, but its use differs . Theoretical air-fuel ratio Engine EC U Heate r Protective cover OPERATION The zirconia element type oxygen sensor operates on the principle that a voltage will be generated if the difference in the oxygen concentration inside and outside the sensor is great . In the lean mixture sensor, however, a voltage applied to the zirconia element when the temperature is high (650°C [1202°F] or greater), results in a current flow with a value which is proportional to the oxygen concentration in the exhaust gas . In other words, when the air-fuel mixture is rich, there will be no oxygen in the exhaust gas, so no current will flow through the zirconia element. When the air-fuel mixture is lean, on the other hand, there will be a lot of oxygen in the exhaust gas and the amount of current flowing through the zirconia element will be large, as shown in the following graph . The lean mixture sensor has been adopted to assure that the air-fuel ratio is kept within a predetermined range, thereby improving fuel economy as well as drivability . This sensor also comes with a heater to heat the zirconia element . The heater is controlled in the same way as the heater of the oxygen sensor . For further details, see page 114 . ELECTRICAL CIRCUITR Y Lean mixture sensor OHP 2 8 REFERENCE When the air-fuel mixture is extremely lean (about 20:1), combustion will be accompanied by reductions in NOx (oxides of nitrogen), CO, and HC (hydrocarbon gas), as shown in the graph below . This is a good thing up to a point. However, if the air-fuel mixture is too lean, not only will HC concentrations increase, but the engine will lose power and/or misfire . CO HC (%) I (PPM 12 ~ 8 d 4 600 400 20 0 0 \ \HC \ \ \~ CO \ \ NOx ❑ NOx (PPM) 300 0 2000 1000 10 12 14 16 18 20 22 0 Richer- Air-fuel ratio~Leaner OHP 28 33 ELECTRONIC CONTROL SYSTEM - Vehicle Speed Senso r VEHICLE SPEED SENSOR This sensor senses the actual speed at which the vehicle is traveling . It outputs an SPD signal, which is used mainly to control the ISC system, and to control the air-fuel ratio during acceleration, deceleration, etc . There are four types of speed sensor :  Reed switch type  Photocoupler typ e  Electromagnetic pickup typ e  MRE (magnetic resistance element) typ e 1 . REED SWITCH TYP E This sensor is mounted in the analog combination meter. It contains a magnet which is rotated by the speedometer cable, turning the reed switch on and off. The reed switch goes on and off four times each time the speedometer cable rotates once . The magnet has the polarities shown in the figure below. The magnetic force at the four areas of transition between the N and S poles of the magnet opens and closes the contacts of the reed switch as the magnet rotates . Q To speedometer cabl e OHP 2 9 ELECTRICAL CIRCUITRY Engine ECU 2 . PHOTOCOUPLER TYP E This sensor is mounted in the combination meter. It includes a photocoupler made from an LED, which is aimed at a phototransistor . The LED and phototransistor are separated by a slotted wheel, which is driven by the speedometer cable . The slots in the slotted wheel generate light pulses as the wheel turns, with the light emitted by the LED divided into 20 pulses for each revolution of the cable . These 20 pulses are converted to four pulses by the digital meter computer, then sent as signals to the ECU . Slotted wheel OHP 29 ELECTRICAL CIRCUITR Y +B Combination meter Puls e Phototransistor conversio n circuit Engine EC U OHP 2 9 34 OHP 29 ELECTRONIC CONTROL SYSTEM - Vehicle Speed Senso r 3 . ELECTROMAGNETIC PICKUP TYP E This sensor is fitted to the transmission and detects the rotational speed of the transmission output shaft . This sensor consists of a permanent magnet, a coil, and a core. A rotor with four teeth is mounted on the transmission output shaft . Rotor N S i Magnet OHP 3 0 +V OHP 30 0 -V ELECTRICAL CIRCUITRY OHP 3 0 Engine ECU OHP 3 0 OPERATION When the transmission output shaft rotates, the distance between the core of the coil and the rotor increases and decreases because of the teeth . The number of lines of magnetic force passing through the core increases or decreases accordingly, and AC (alternating current) voltage is generated in the coil . Since the frequency of this AC voltage is proportional to the rotational speed of the rotor, it can be used to detect the vehicle speed . OHP 3 0 ® Coil Core Speed sensor 35 F* ELECTRONIC CONTROL SYSTEM - Vehicle Speed Senso r 4 . MRE (MAGNETIC RESISTANCE ELEMENT) TYP E This sensor is mounted on the transmission or the transfer and is driven by the drive gear of the output shaft . Speed sensor OHP 3 1 This sensor consists of an HIC (hybrid integrated circuit) with a built-in MRE (magnetic resistance element) and a magnetic ring . OHP 3 1 OPERATION The resistance value of the MRE changes accor- ding to the direction of the lines of magnetic force applied to it . Thus, the direction of the lines of magnetic force is changed by the rotation of the magnet fitted to the magnetic ring with the result that the output of the MRE becomes an alternating waveform as shown in the illustration on the above right . The comparator in the speed sensor converts the alternating waveform into a digital signal, which is then inverted by the transistor before being sent to the combination meter, as shown in the illustration at right above . The frequency of the waveform is in accordance with the number of poles of the magnet fitted to the magnetic ring . There are two types of magnetic ring (depending on the vehicle model) : the type with twenty magnetic poles, and the type with four magnetic poles . The 20-pole type generates a 20-cycle waveform (i .e., twenty pulses for each rotation of the magnetic ring), while the 4-pole type generates a 4-cycle waveform . Constant voltage circuit, + B 20-POLE TYPE SPEED SENSO R Magnetic ring (rotating ) MRE output N S N Comparator 1 output 0 Speed 12 V~ sensor 0 V output OHP 3 1 In the 20-pole type, the frequency of the digital signal is converted from twenty pulses for each revolution of the magnetic ring to four pulses by the pulse conversion circuit in the combination meter, then the signal is sent to the Engine ECU . (See electrical circuitry at right . ) In the case of the 4-pole type, there are two different kinds: in one type, the signal from the speed sensor passes through the combination meter before going to the Engine ECU ; in the other type, this signal goes directly to the Engine ECU without passing through the combination meter. (See electrical circuitry at right . ) 36 ELECTRONIC CONTROL SYSTEM - Vehicle Speed Senso r The output circuitry of the speed sensor differs depending on the vehicle model. As a result, the output signal also differs depending on the model : one type is the output voltage type and the other is the variable resistance type . The types of MRE-type speed sensor presently used by Toyota are shown in the following table . (As of Mar., 1991 ) TYPE OF TYPE OF SIGNA L MAGNETIC RIN G C 20-pole type (20 pulses/rev .) Output voltage typ e 5-12V ) (0V H 4-pole type 30, (4 pulses/rev .) Variable resistanc e type (0 12 H - ) REFERENCE Comparator The comparator circuit selects either of the two input voltages as the reference voltage and then compares the reference voltage with the other input voltage to judge which is larger or smaller. If input voltage 'B` is taken as the reference voltage in the example circuit shown below, the relationship between the input and the output becomes as follows : Output OHP 32 INPUT OUTPUT A> B Hi (1 ) A < B Lo (0 ) OHP 3 2 The speed sensor uses this function to convert the alternating waveform into a digital signal : 1 OHP 32 ELECTRICAL CIRCUITRY -11-` 20-pole type (output voltage type) ® 20 pulses 4 pulses Engine EC U Speed Combination n sensor 111111111111 mete r 4-pole type (output voltage type ) 4 pulses 4 pulses Speed Combinatio n sensor -1 LJL mete r Input circui t C 4-pole type ( variable resistance type) OHP 3 3 Engine ECU OHP 3 3 OHP 3 3 37 ELECTRONIC CONTROL SYSTEM - STA Signal, NSW Signa l STA (STARTER) SIGNA L This signal is used to judge if the engine is being cranked. Its main function is to allow the Engine ECU to increase the fuel injection volume during cranking. As can be understood from the figure below, the STA signal is voltage the same voltage as that supplied to the starter motor . ELECTRICAL CIRCUITRY Ignition (M/T ) switch Engine ECU OHP 34 NSW (NEUTRAL START SWITCH) SIGNAL In vehicles with an automatic transmission or transaxle, this signal is used by the Engine ECU to determine whether the shift lever is in the "P" or "N" position, or in some other position . The NSW signal is used mainly in controlling the ISC system . ELECTRICAL CIRCUITRY Engine ECU OHP 3 4 REFERENCE 1 . The Engine ECU judges whether the engine is cranking based on the STA signal. There are also engines which use the NE signal to judge the engine running conditions during starting . 2 . In some engine models, if the STA signal is input while the engine is running, it could result in the engine stalling . 1 . When the ignition switch is in the START position, battery voltage is supplied to the NSW terminal . 2 . When the ignition switch is in a position other than START, and the neutral sta rt switch is open ( i .e., the transmission is in "L", "2", "D" or "R"), the voltage at the NSW terminal is high . 3 . When the ignition switch is in a position other than START, and the neutral sta rt switch is closed (i .e., the transmission is in "P" or " N"), the voltage at the NSW terminal is low due to the electrical load at the starter motor, etc . 38 ELECTRONIC CONTROL SYSTEM - A/C Signal, Electrical Load Signa l A/C (AIR CONDITIONER) SIGNAL This signal senses when the air conditioner magnetic clutch is on or air conditioner switch is on . This signal is used to control the ignition timing during idling, and to control the ISC system, the fuel cut-off speed, and other functions . ELECTRICAL CIRCUITRY Engine ECU ELECTRICAL LOAD SIGNAL 1* This signal detects when the head lamps, rear window defogger, etc., are on . Depending on the vehicle model, the circuitry for this signal can have a number of electrical load signals which are brought together and input into the Engine ECU as a single signal, as shown in the following electrical circuit, or it can have each signal input to the Engine ECU separately . This signal is used for control of the ISC system . ELECTRICAL CIRCUITR Y A/C magnetic clutch C OHP 3 4 A/C amplifie r A/C switch 0 A/C Engine ECU Engine EC U OHP 34 39 13 ELECTRONIC CONTROL SYSTEM - Fuel Control Switch or Connector, EGR Gas Temperature Senso r FUEL CONTROL SWITCH OR CONNECTOR EGR GAS TEMPERATURE SENSOR This switch or connector informs the Engine ECU whether the gasoline being used is regular or premium . This signal is used mainly in controlling the ESA system . The Engine ECU has two sets of advance angle data for different types of gasoline (regular or premium) . If the Engine ECU judges that regular gasoline is being used, it uses the data for the smaller angle of advance . If it judges that premium gasoline is being used, it uses the data for the larger angle of advance . ELECTRICAL CIRCUITRY Engine ECU This sensor is mounted in the EGR valve . It detects the temperature of the EGR gas. This sensor is composed of a thermistor, and it resembles the water temperature sensor or intake air temperature sensor . The signals from this sensor are used in the diagnostic system . When this sensor detects EGR gas temperatures below a predetermined level during EGR system operation, the Engine ECU judges that the EGR system is malfunctioning and lights the "CHECK ENGINE" lamp to inform the driver . ELECTRICAL CIRCUITRY Engine ECU OHP 3 5 I NOTE Fuel Control Connecto r In some vehicle models, this connector should be connected when permium gasoline is used, and disconnected when regular gasoline is us- ed . In other models, the situation is the op- posite . Refer to the owner's manual for the location of the connector and the changeover procedure between regular gasoline and premiu m gasoline . Fuel control connector OHP 35 REFERENCE Some recent D-EFI systems do not use an EGR gas temperature sensor . In these systems, EGR operation is checked by detecting fluctuations in the intake manifold pressure with a manifold pressure sensor (vacuum sensor) . \1 40 ELECTRONIC CONTROL SYSTEM - Variable Resisto r VARIABLE RESISTO R This resistor is provided in D-type EFI systems and L-type EFI with optical Karman vortex type air flow meter or hot-wire type air flow meter which are not equipped with an oxygen sensor . It is used to change the air-fuel ratio of the idle mixture . OHP 35 Turning the idle mixture adjusting screw clockwise moves the contacts inside the resistor, raising the VAF terminal voltage . Conversely, turning the screw counterclockwise lowers the VAF terminal voltage . When the VAF terminal voltage rises, the Engine ECU increases the injection volume slightly, making the air-fuel mixture a little richer . ELECTRICAL CIRCUITRY Engine ECU OHP 35 ® NOTE It is usually not necessa ry to adjust the idle mixture in most models, provided that the vehicle is in good condition . However, if it does become necessary to do so, always use a CO meter. If a CO meter is not available, it is best not to attempt to adjust the idle mixture if at all possible . 1 1 . In the vane type air flow meter, the idle mix- ture can be adjusted by turning the idle mix- ture adjusting screw in the air flow meter . (Some engines are equipped with air flow meters which are sealed with an aluminum plug . ) REFERENCE Idle mixture adjusting scre w In D-type EFI systems and L-type EFI with optical Karman vortex type air flow meter or hot-wire type air flow meter with an ox- ygen sensor, the ECU uses the signals from the oxygen sensor to correct the air-fuel ratio of the idle muxture, so there is no separate device for adjusting the idle mix- ture . 41 13 ELECTRONIC CONTROL SYSTEM - Kick-down Switch , Water Temp . Switch, Clutch Switc h KICK-DOWN SWITCH* WATER TEMPERATUR E The kick-down switch is fitted to the floor panel SWITC H directly under the accelerator pedal . When the This switch sends signals to the Engine ECU accelerator pedal is depressed beyond the full when the engine is about to overheat . When the throttle opening level, the kick-down switch Engine ECU receives this signal, it controls the turns on and sends a KD signal to the ECU . This EFI system and air conditioner cut-off control KD signal is used for power enrichment. system in order to lower the fuel combustion *This switch is also called the "full throttle switch" in other manuals . ~- -~ temperature . ELECTRICAL CIRCUITRY Engine EC U Accelerato r e----peda l Kick-down switch OHP 3 6 ACCELE- Kick-dow n RATOR switc h PEDAL ~ . r Accelerato r ITEM peda l THROTTLE Fully Fully Fully VALVE closed opened opene d KICK-DOW N SWITCH Off Off On OHP 3 6 CLUTCH SWITCH The clutch switch is located under the clutch pedal, and is used to detect whether or not the clutch has been applied . This signal is used mainly to control the fuel cut-off engine speed (See page 78), thereby reducing emissions . ELECTRICAL CIRCUITRY Engine ECU ELECTRICAL CIRCUITRY Engine ECU OHP 3 6 OHP 3 6 42 ELECTRONIC CONTROL SYSTEM - Knock Senso r KNOCK SENSOR The knock sensor is mounted on the cylinder block and detects knocking in the engine . Low- Frequency - High ELECTRICAL CIRCUITRY OHP 3 7 Engine ECU OHP 37 When engine knocking occurs, the Engine ECU uses the KNK signal to retard the ignition timing in order to prevent the knocking . This sensor contains a piezoelectric element which generates a voltage when it becomes deformed as a result of cylinder block vibration due to knocking . Diaphrag m AM l Piezoelectric element OHP 3 7 Since the engine knocks at a frequency of approximately 7 kHz, the voltage output by the knock sensor is at its highest level at about that frequency . There are two types of knock sensor . One type generates high voltages over a narrow range of vibration frequencies, while the other type generates high voltages over a wide range of vibration frequencies . OHP 3 7 REFERENCE The Engine ECU judges whether the engine is knocking by measuring whether the KNK signal voltage has peaked above a certain voltage level or not . When the Engine ECU judges that the engine is knocking, it retards the ignition timing . When the knocking stops, the ignition timing is advanced again after a predetermined period of time . Strong Ignition Weak Ignitio n KNK SIGNAL Time- 43 ELECTRONIC CONTROL SYSTEM - HAC Sensor, Vapor Pressure Sensor, Turbocharging Pressure Senso r HAC (HIGH-ALTITUDE COMPENSATION) SENSOR The HAC sensor senses changes in the at- mospheric pressure . Its construction and opera- tion are the same as those of the manifold pressure sensor (See page 17) . This sensor can be mounted either in the Engine ECU, or in the passenger compartment separately from the Engine ECU . Currently, the type mounted in the Engine ECU is used the most . When driving at high altitudes, there is not only a decrease in the atmospheric pressure, but also a drop in the density of the intake air . As a result, the air-fuel ratio deviates toward the rich side in engines with L-type EFI (excluding hot-wire type air flow meters) . The HAC sensor corrects for these deviations in the air-fuel ratio . ELECTRICAL CIRCUITR Y (type with sensor mounted separately ) HAC sensor Engine ECU TURBOCHARGING PRESSURE SENSO R The turbocharging pressure sensor senses the turbocharging pressure ( intake manifold pressure) . Its construction and operation are the same as those of the manifold pressure sensor (See page 17) . If the turbocharging pressure becomes abnormally high, the Engine ECU cuts off the supply of fuel to protect the engine . Silicon chi p f intake manifold pressure OHP 38 (V) 5 4 3 t Atmospheric pressure OHP 3 8 VAPOR PRESSURE SENSO R Basic operation and construction is the same as that of a manifold pressure sensor or turbocharg- ing pressure sensor . Output characteristics differ, however, to enable the detection of small changes in vapor pressure . (V ) 44 5 4 3 2 1 k 0 1 -3 . 5 (-26) Atmospheric pressur e 0 +1 .5 (0) (+11) Pressure kPa (mmHg) 2 1 0 13 100 200 kPa (100, 3 .9) (750, 29.5) (1500, 59.1) (mmHg, in.Hg) Turbocharging pressure (absolute pressure) OHP 38 ELECTRICAL CIRCUITRY Turbocharging pressure sensor Engine ECU ELECTRONIC CONTROL SYSTEM - Stop Lamp Switch, Oil Pressure Switch, Communications Signal s STOP LAMP SWITC H This signal is used to detect when the brakes have been applied . The STP signal voltage is the same as the voltage supplied to the stop lamps, as seen in the diagram below . The STP signal is used mainly to control the fuel cut-off engine speed . (The fuel cut-off engine speed is reduced slightly when the vehicle is braking . ) ELECTRICAL CIRCUITR Y ~Stop lamp switch STP or BR K Lamp failure; relay' - - Engine ECU Stop lamps L _____J * Some vehicle models only OHP 3 9 OIL PRESSURE SWITC H This signal is used to judge whether the engine oil pressure is low or high . The oil pressure signal is used mainly in controlling the ISC system . ELECTRICAL CIRCUITRY COMMUNICATIONS SIGNALS © Communications signals are signals that are sent between different ECUs to make it possible for them to coordinate their operations . These communications signals are explained below . 1 . THROTTLE OPENING ANGLE SIGNAL S The throttle opening angle (VTA) signal from the throttle position sensor is processed by the Engine ECU, then sent to the ECT ECU, Suspension ECU, etc ., as combinations of the L1, L2, and L3 signals . ELECTRICAL CIRCUITR Y ECT ECU Engine ECU OHP 39 2 . THROTTLE OPENING ANGLE SIGNALS FOR TRC (TRACTION CONTROL) SYSTEM These signals are the throttle opening angle (VTA1 and VTA2) signals which are input from the main and sub throttle position sensors, then passed on by the Engine ECU to the TRC ECU . ELECTRICAL CIRCUITRY TRC ECU Engine EC U VTH VTH VSH VSH 01 VTA 1 OHP 39 45 ELECTRONIC CONTROL SYSTEM - Communications Signal s 3 . CRUISE CONTROL SYSTEM COMMUNICATIONS SIGNA L This signal is the ignition timing retard request signal that is sent from the Cruise Control ECU to the Engine ECU . ELECTRICAL CIRCUITRY OHP 4 0 4 . TRC SYSTEM COMMUNICATIONS SIGNA L This signal is sent from the TRC ECU to the Engine ECU to inform it that traction control is in operation . When the TRC ECU outputs the TR signal, the Engine ECU executes various types of corrections related to traction control, such as retarding the ignition timing . ELECTRICAL CIRCUITR Y TRC ECU Engine EC U OHP 40 5 . ABS (ANTI-LOCK BRAKE SYSTEM) COMMUNICATIONS SIGNA L This signal detects when the ABS system is operating . It is used in fuel cut-off control to reduce the effectiveness of engine braking as necessary . ELECTRICAL CIRCUITR Y ABS ECU Engine EC U OHP 4 0 6. INTERCOOLER SYSTEM WARNING SIGNA L When trouble occurs in the intercooler system in vehicles equipped with a turbocharging system having a water-cooled type intercooler, the Intercooler ECU sends this signal to the Engine ECU, which lights the "CHECK ENGINE" lamp . ELECTRICAL CIRCUITR Y Intercooler ECU Engine EC U OHP 40 46 ELECTRONIC CONTROL SYSTEM - Communications Signal s 7 . EHPS (ELECTRO-HYDRAULIC POWER STEERING) SYSTEM COMMUNICA- TIONS SIGNAL When the engine coolant temperature or the engine speed is extremely low, the load on the alternator could become excessive when the vane pump motor of the EHPS is driven . To prevent this, the Power Steering ECU sends this signal to the Engine ECU, which therefore causes the ISC to increase the engine speed . ELECTRICAL CIRCUITR Y Power Steering ECU Engine EC U OHP 4 1 REFERENCE EHPS is a type of power steering in which the vane pump is driven by an electric motor . 8 . ENGINE SPEED SIGNAL This is the NE signal, which is input to the Engine ECU, then undergoes waveform shaping and is output to the TRC ECU, etc . ELECTRICAL CIRCUITR Y TRC ECU Engine ECU OHP 41 9 . ENGINE IMMOBILISER SYSTEM COM- MUNICATIONS SIGNA L The Engine ECU generates a rolling code based on certain parameters, and sends it to the Transponder Key ECU ( IMO terminal) . Upon receiving the rolling code from the Engine ECU, the Transponder Key ECU converts the roll- ing code according to certain parameters, and sends it to the Engine ECU (IMI terminal) . If the correct signal is not sent by the Transponder Key ECU, the Engine ECU will prohibit fuel injec- tion and IGT signal, thus disabling the engine . ELECTRICAL CIRCUITR Y Transponder Key ECU EFII IMO Engine ECU EFIO IMI 47 ELECTRONIC CONTROL SYSTEM - Diagnostic Terminal (S ) DIAGNOSTIC TERMINAL(S ) The T or TE1 terminal is located in the check connector in the engine compartment and the TE1 and TE2 terminals are located in the TDCL (Toyota diagnostic communication link) in the passenger compartment ( located under the instrument panel) . I Check connecto r , OHP 41 NOTE OBD-II compatible engines of vehicles sold in the U .S.A . and Canada are equipped with a DLC3 in addition to the check connector (DLC1 ; Data Link Connector 1) and TDCL (DLC2) . Consequently, it does not have a TE2 terminal of DLC1 or TE2 or TE1 terminal of DLC2 . In addition, in case of reading diagnostic codes, the tester for exclusive use* must be connected to DLC3 . For further details, see page 137-2 . OBD-II scan tool or TOYOTA hand-hel d tester TDCL OHP 4 1 When these terminals are connected with the E1 terminal, diagnostic codes for either the normal mode or the test mode can be read from the blinking of the "CHECK ENGINE" lamp in the combination meter. For fu rther details, see page 159 . ELECTRICAL CIRCUITRY Check connecto r El Engine EC U OHP 4 1 REFERENCE 1 . The TDCL is provided in some vehicl e models equipped with the TCCS type engine control system . 2 . In some vehicle models, the TE2 terminal is located in the check connector . DLC 3 ELECTRICAL CIRCUITR Y 48 EFI - Genera l EFI (ELECTRONIC FUEL INJECTION ) GENERAL The Engine ECU calculates the basic fuel signal . It bases its calculations on a program injection duration in accordance with two stored in its memo ry . signals: 1) the intake manifold pressure signal (in The Engine ECU also determines the optimum D-type EFI) from the manifold pressure sensor, fuel injection duration for each engine condition or the intake air volume signal (in L-type EFI) based on signals from various other sensors . from the air flow meter, and 2) the engine spee d Air cleaner Pressure regulator Manifold pressure senso r Engine EC U Engine speed Sensors Fuel filter Fuel tank (with built-in fuel pump ) OHP 42 BASIC CONSTRUCTION OF D-TYPE EFI SYSTE M Engine EC U Engine speed Sensors BASIC CONSTRUCTION OF L-TYPE EFI SYSTEM 49 EFI - Genera l The following table shows the specifications for their differences only are covered . If there is a the 4A-FE engine. Items marked with a circle in circle in the "STEP 2 (EFI)" column in the the "APPENDIX" column are included in the following table, refer to the Training Manual for specifications for each engine in the APPENDIX Step 2, vol . 5 (EFI), for a detailed explanation for section (page 188) in the back of this manual . the relevant items . Those items covered in Step 2, vol . 5 (EFI), are covered in outline form only in this manual, o r PAG E EFI (ELECTRONIC FUEL INJECTION) (THIS ITEM REMARK APPENDIX STEP 2 MANUAL) (EFI ) D-type EFI (manifold 52 0 T f EFI pressure control type ) ypes o L-type EFI (air flow control 5 2 type ) Fuel In-tank type 54 0 pump In-line type 54 On-off control (by ECU) 55 J On-off control (by fuel pump 56 switch ) Fuel pump By engine EC U control On-off with fuel pump 5 7 control control relay an d with resisto r speed By engine EC U control w ith fuel pump 5 7 ECU Fuel filter 58 0 E Pulsation damper 58 Pressure Normal type 58 0 regulator Pressure-up control system 58 Injectors 59 0 High-resistance 60 O Injector Voltage- injector s drive control Low-resistanc e method injectors 60 Current control 6 1 Cold start injector 6 2 Start injector time switch 6 2 Cold start Controlled by start injector 6 3 injector time switc h electrica l circuitry Controlled by ECU 6 3 Throttle body 65 0 Air induction Air Wax type 6 5 system valve Bi-metal type 6 5 * Specifications for Corolla 4A-FE engine (Apr ., 1992) (Continued on next page ) 50 EFI - Genera l PAGE STEP 2 EFI (ELECTRONIC FUEL INJECTION) (THIS ITEM* REMARK APPENDIX (EFI ) MANUAL ) Simultaneous 66 Fuel 2 groups 66 ~ i injection methods 3 groups 6 7 and 4 groups 6 7 injection timing Independent 6 7 For 1 S-i 6 7 Start injection control 70 ~ Basic For D-type EFI 7 1 injectio n duratio n control For L-type EFI 7 2 Intake air temp. correction 7 2 After-start enrichment 73 U Warm-up enrichment 73 ~ Power enrichment 74 0 Air-fuel Acceleratio n o ratio enrichment 74 0 C correction correction 0 during Deceleration 74 c transition lean correctio n 0 ~ After- Air fuel Oxygen sensor 75 ~ With TW C start :3 ratio n -0 injection feedback Lean mixture 7 5 o control correction senso r ~ CO emission control 76 ~ Except with oxyge n ~ correction senso r Idling stability 77 0 LL correctio n High-altitude com- 77 pensation correctio n During 78 0 deceleration Fuel At high engine 78 0 cut-off speed s At high vehicle 7 8 speeds Voltage correction 79 0 * Specifications for Corolla 4A-FE engine (Apr ., 1992) 51 0 TYPES OF EFI EFI - Types of EF I EFI systems can be divided into two types according to the method used to sense the volume of intake air : 1 . D-TYPE EFI (MANIFOLD PRESSURE CONTROL TYPE ) This type measures the strength of the vacuum in the intake manifold, thereby sensing the volume of air by its density . Ai r INTAKE MANIFOL D MANIFOLD PRESSURE SENSO R 1 I/ F i Detection of intake manifold pressure ENGIN E Engine speed I Fuel AIR FLOW METE R INTAKE MANIFOL D ENGIN E Engine spee d ENGINE ECU Injectio n INJECTOR Injection volume &-- Fuel control OHP 43 Vane type ENGINE ECU Injection volume control OHP 4 3 MANIFOLD PRESSURE SENSOR OHP 43 2 . L-TYPE EFI (AIR FLOW CONTROL TYPE ) This type directly senses the amount of air flowing into the intake manifold by means of an air flow meter . Hot-wire type AIR FLOW METE R Injection INJECTOR Optical Karman vortex typ e Detection of intake air volume OHP 4 3 OHP 4 3 52 EFI - Fuel System FUEL SYSTEM Fuel pumped out of the fuel tank by the fuel pump passes through the fuel filter, then is sent to the injectors . The fuel pressure at the injectors is maintained at a constant high level (285 kPa [2 .9 kgf/cm2; 41 .2 psi] or 250 kPa [2 .55 kgf/cmz; 35 .5 psi], depending on the engine model), which is greater than the intake manifold pressure. When fuel is injected, the fuel pressure in the fuel line changes slightly . Some engines are equipped with a pulsation damper to prevent this from occurring . One injector is mounted in front of each cylinde r Injectors ------ » --------T r-REFERENC E 1 . Multi-point Injectio n Each cylinder has its own injector, and fuel is injected in front of the intake ports near the cylinders. This is the method used in most EFI engines . Xb Solenoid resistor* (except in the case of the single-point injector for the 1S-i engine), and the amount of fuel injected is controlled by the length of time current is sent to the injectors . A single cold start injector is also mounted in the intake chamber to improve startability in cold weather. (This system is not included in some engines . ) The injection duration of the cold start injector is controlled by a start injector time switch . (In some engines, it is controlled by both the ECU and the start injector time switch . ) lC Pressure regulato r Cold start injector* 2. Single-point Injection ( Central Injection) The single injector is mounted in the throttle body and fuel is injected at this point into the intake air stream . This method is used in the 1S-i engine only . 53 0 EFI - Fuel Syste m 1 . FUEL PUM P IN-TANK TYPE IN-LINE TYP E This type of fuel pump is mounted inside the fuel This type of fuel pump is mounted outside the tank. fuel tank . This type is no longer in use at Toyota . This type produces much less pulsation an d noise the in-line type . Currently, only this type is used in Toyota vehicles . OHP 45 Motor Silencer Diaphragm - chambe r Check valve - Brush Armature Magnet Pump space r Relief valv e Filter Mj5LX ]TER--A 00 Roto r OHP 45 Outlet Inlet t - it Casin g Impeller Blade OHP 45 OHP 4 5 54 EFI - Fuel Syste m 2 . FUEL PUMP CONTRO L The fuel pump in a vehicle equipped with an EFI engine operates only when the engine is running. This is to prevent fuel from being pumped to the engine when the ignition switch is on but the engine is stopped . The following types of fuel pump control are in use at present : On-off contro l Fuel pump control method L I On-off L control with speed control By Engine ECU By fuel pump switc h By Engine ECU, fuel pump control relay and resistor By Engine ECU and fuel pump ECU ON-OFF CONTROL (BY ENGINE ECU) * 1) Engine cranking When the engine is cranking, current flows from the IG terminal of the ignition switch to the Li coil of the EFI main relay, turning the relay on . At the same time, current flows from the ST terminal of the ignition switch to the L3 coil of the circuit-opening relay, turning it on to operate the fuel pump . Battery The starter operates next and the engine begins to crank, at which point the Engine ECU receives an NE signal . This signal causes the transistor inside the Engine ECU to go on, and current therefore flows to the L2 coil of the circuit- opening relay . ~2 Engine started After the engine sta rts and the ignition switch is returned from the START position ( ST terminal) to the ON position (IG terminal), current flowing to the L3 coil of the circuit-opening relay is cut off. However, current continues to flow to the L : coil, while the engine is running, due to the transistor inside the Engine ECU being on . As a result, the circuit-opening relay stays on, allowing the fuel pump to continue operating . ($) Engine stopped When the engine stops, the NE signal to the Engine ECU stops . This turns off the transistor, thereby cutting off the flow of current to the L2 coil of the circuit-opening relay . As a result, the circuit-opening relay turns off, turning off the fuel pump . D-EFI systems and L-type EFI with optical Kar- man vortex type air flow meter or hot-wire type air flow meter . 55 ❑ ~► REFERENCE Circuit-opening Relay EFI - Fuel System The resistor R and the capacitor C in the circuit-opening relay are for the purpose of preventing the relay contacts from opening when current stops flowing in coil L2 due to electrical noise (fuel pumps controlled by the ECU) or to sudden drops in the intake ai r ON-OFF CONTROL (BY FUEL PUMP SWITCH) * ~) Engine cranking When the engine is cranking, current flows from the IG terminal of the ignition switch to the Li coil of the EFI main relay, turning the relay on . Current also flows from the ST terminal of the ignition switch to the La coil of the circuit- opening relay, turning it on to operate the fuel pump. After the engine starts, the cylinders begin drawing in air, causing the measuring plate inside the air flow meter to open . This turns on the fuel pump switch, which is connected to the measuring plate, and current flows to the Lz coil of the circuit-opening relay . ~2 Engine sta rt ed After the engine sta rts and the ignition switch is turned from START back to ON, current flowing volume ( fuel pumps controlled by fuel pump switch) . They also serve to prevent sparks from being generated at the relay contacts . On some recent models, an L3 coil is not provided in the circuit-opening relay . to the La coil of the circuit-opening relay is cut off. However, current continues to flow to the Ls coil, while the engine is running, due to the fuel pump switch inside the air flow meter being on . As a result, the circuit-opening relay stays on, allowing the fuel pump to continue operating . ~3 Engine stopped When the engine stops, the measuring plate completely closes and the fuel pump switch is turned off. This cuts off the flow of current to the Ls coil of the circuit-opening relay . As a result, the circuit-opening relay goes off and the fuel pump stops operating . L-type EFI with vane type air flow meter . Check (m pT~ Circuit-opening rela y connector Battery 2P fuel pump check connector (some engines only) - IN OHP 4 6 56 EFI - Fuel Syste m ON-OFF CONTROL WITH SPEED CONTROL (BY ENGINE ECU, FUEL PUMP CONTROL RELAY AND RESISTOR ) The basic operation of this system is the same as that of the previously-mentioned on-off type fuel pump control system, but in this system, the ECU changes the speed of the fuel pump in two stages corresponding to the amount of fuel required by the engine . With this system, electric power consumption is reduced and fuel pump durability is improved . ~ At low speed s When the engine is idling, or under normal driving conditions (that is, when a small amount of fuel is satisfactory), the Engine ECU turns on the fuel pump control relay. The point of this relay contacts contact B, and the current to the fuel pump flows through a resistor, causing the fuel pump to run at low speed . Fuel pump control rela y Engine EC U c?i At high speed s When the engine is operating at high speeds or under heavy loads, the Engine ECU turns off the fuel pump control relay . The point of this relay con- tacts contact A, and the current to the fuel pump flows directly to the pump without passing through the resistor, causing the fuel pump to run at high speed . The fuel pump also runs at high speed while the engine is starting . Fuel pump control relay Engine ECU Fuel FP pump ® High speed ON-OFF CONTROL WITH SPEED CONTROL (BY ENGINE ECU AND FUEL PUMP ECU ) The basic operation of this system is the same as the types that have been explained thus far . In this system, however, on-off control and speed control of the fuel pump is performed entirely by the Fuel Pump ECU based on the signals from the Engine ECU . The Fuel Pump ECU is wired as shown in the following diagram . Signals from this ECU are used to switch the fuel pump speed back and forth bet- ween 2 steps . In addition, the Fuel Pump ECU is equipped with a fuel pump system diagnosis func- tion . When trouble is detected, signals are sent from the DI terminal to the Engine ECU . 57 3 . FUEL FILTER EFI - Fuel Syste m The fuel filter filters out dirt and other foreign particles from the fuel . Out Q Q In 4. PULSATION DAMPER OHP 4 8 The pulsation damper absorbs variations in fuel line pressure by means of a diaphragm . Delive ry pipe OHP 4 8 REFERENCE In the 4A-FE engine and some other engine models, the pulsation damper is no longer necessary because the fuel line has been simplified . 5 . PRESSURE REGULATOR The pressure regulator regulates the fuel pressure to the injectors in accordance with the intake manifold pressure . 4 To fuel return hos e PRESSURE-UP CONTROL SYSTEM OHP 48 In some engines, the fuel pressure is increased by the Engine ECU when the temperature of the coolant or ambient temperature of the engine is too high during engine cranking . The Engine ECU causes more air to be drawn into the chamber of the pressure regulator to increase the fuel pressure . This prevents vapor lock at high engine temperatures in order to help the engine start when it is warm . From delivery~> pipe Some models only OHP 4 8 58 EFI - Fuel Syste m If the engine is cranked when the coolant temperature is 100°C (212°F) or higher, the Engine ECU turns on the VSV (the exact temperature depends on the engine model) . When the VSV goes on, atmospheric air is introduced into the diaphragm chamber of the pressure regulator, causing the fuel pressure to become higher than that under normal engine operating conditions . After the engine is started, the VSV remains on for about two minutes . There are some engine models in which a water temperature sensor (THW) is used instead of a water temperature switch (TSW) . There are also engines in which other signals besides the coolant temperature are used in pressure-up control . These signals include the intake air temperature (THA) signal, the intake air volume (VS or PIM) signal, and the engine speed (NE) signal . 101 .3 (1 kgf/cmz ) 0 NOTE 1 . On some recent models, intake manifol d pressure is not connected to the pressure regulator . Fuel pressure is always maintained at a con- stant pressure higher than the atmospheric pressure . As a result, changes in injection volume caused by intake manifold pressure are corrected by the Engine ECU . VSV: on OHP 48 2 . In addition to the models described in 1 above, there are also models in which the pressure regulator is provided in the fuel tank . Since there is no fuel return pipe, it becomes difficult for air bleed once it has entered the fuel pipe . It is for this reason that more time is required to start the engine after the fuel fiiter or similar compo- nent has been replaced . 6. INJECTORS The injector is an electromagnetically-operated nozzle which injects fuel in accordance with signals from the ECU . Inlet 4 SIDE-FEED TYPE TOP-FEED TYPE OHP 4 9 ,,-- wv I Internal Resistance of Injector There are two types of injector, which differ in their internal resistance level :  High-resistance type: approx . 13 .8 Q  Low-resistance type : approx. 1 .5 ^- 3 Sd 59 EFI - Fuel System 7 . INJECTOR DRIVE METHOD S There are two injector drive methods . One is the voltage control method, and the other is the current control method . High-resistance injectors (Most engines ) Voltage contro l Injector drive method Low-resistance injectors (Some engines) VOLTAGE CONTROL METHOD FOR LOW- RESISTANCE INJECTORS The electrical circuitry for this type of injector, as well as its operation, are basically the same as for the high-resistance injector, but since a low-resistance injector is used, a solenoid resistor is connected between the ignition switch and the injectors . The electrical circuitry for simultaneous injection (See page 66) is shown below . Ignition switc h Current control Low-resistance injectors (No longer in use ) VOLTAGE CONTROL METHOD FOR HIGH- RESISTANCE INJECTOR S Battery voltage is applied to the injectors directly via the ignition switch . When the transistor (Tr) in the Engine ECU goes on, current flows from terminals No . 10 and No . 20 to E01 and E02. While the Tr is on, current flows through the injectors and fuel is injected . The electrical circuitry for simultaneous injection (See page 66) is shown below. Ignition switch OHP 49 OHP 49 60 EFI - Fuel Syste m CURRENT CONTROL METHOD (for 4A-GE engine with D-type EFI) In injectors that use this method, the solenoid resistor is eliminated, and a low-resistance injector is connected directly to the battery . Current flow is controlled by switching a transistor in the Engine ECU on and off . When the injector plunger is pulled in, a heavy current flows, causing the amperage to rise quickly . This causes the needle valve to open quickly, resulting in improved injection response and reduced ineffective injection duration . While the plunger is held in, the current is reduced, preventing the injector coil from generating heat, as well as reducing power consumption . On Injection Of f signal ~ Voltage 12 V, 20kHz waveform 0V i ~CT B A Amperage waveform ® This current builds up until the potential at point "A" reaches a certain value, then the injector drive circuit switches Tri off . The switching on and off of Tr, is repeated at a frequency of roughly 20 kHz over the duration of the injection . In this way, the current to the injector solenoid coils is controlled (when the +B voltage is 14 V, the current pulling in the injector plunger is approximately 8 A, while it is about 2 A while the plunger is being held in) . Tr2 absorbs counter-electromotive force from the injector solenoid coil while Tri is being switched on and off, thus preventing sudden reductions in current . If an extremely large current flows to the injectors for any reason, the fail-safe main relay goes off, cutting off the flow of current to the injectors . REFERENCE The current control method was used in the 4A-GE engine with D-type EFI, which was produced between August, 1983, and May, 1987 . Ineffective injection duration OHP 50 The drive circuitry for this injector is as shown in the figure at the right. Battery voltage is applied to the ignition switch, then to the fail-safe main relay or INJ fuse, then to the injectors, and finally to the Engine ECU . The fail-safe main relay is connected in such a way that it is grounded through the injector drive circuitry via the FS terminal of the Engine ECU . The relay therefore goes on when the ignition switch is turned on . This turns on Tr, in the Engine ECU, letting current flow to the injector solenoids . Ignition Fail-safe switch main relay * Engine EC U OHP 5 0 *In vehicles produced between August, 1984, and May, 1987, an INJ fuse was used in place of the fail-safe main relay . 61 EFI - Fuel Syste m 8. COLD START INJECTOR 9 . START INJECTOR TIME SWITC H The function of the cold start injector is to The function of the start injector time switch is maintain engine startability when it (the engine) to control the maximum injection duration of the is cold . This injector operates only during cold start injector . cranking when the coolant temperature is low . Inlet Plunger Bi-metal element OHP 50 NOTE On many current engine models, the cold start system has been discontinued . Instead, star- ting injection control, which is under the con- trol of the Engine ECU, controls the injection of fuel during starting . Heat coils Contact s OHP 5 1 62 EFI - Fuel Syste m 10. COLD START INJECTOR ELECTRICAL CIRCUITRY CONTROLLED BY START INJECTOR TIME SWITCH When the engine is cranked while the engine coolant temperature is low, the duration of cold start injector operation is controlled by the start injector time switch . ST terminal CONTROLLED BY ECU (STJ CONTROL ) In order to improve startability when the engine is cold, the injection duration of the cold start injector is controlled not only by the start injector time switch but also by the Engine ECU in accordance with the coolant temperature . Control of the injection duration of the cold start injector continues to be carried out by the start injector time switch, as shown by shaded area A in the figure below, but control is also exercised by the Engine ECU, as shown by shaded area B in the figure . Engine ECU STA STA OHP 5 1 I -20 0 20 40 60 (-4) (32) (68) (104) (140 ) Coolant temperature °C (°F ) On or off depending on engine model OHP 51 U N N C 6- 0 co 4- C 0 a 0 i 2- -S 0 STJ I I STA A, B -20 0 20 40 6 0 (-4) (32) (68) (104) (140) Coolant temperature °C (°F ) A: Controlled by start injector time switch B: Controlled by EC U A, B: Controlled by sta rt injector time switch and ECU OHP 5 1 63 a AIR INDUCTION SYSTEM EFI - Air Induction Syste m This system supplies the air necessary for combustion to the cylinders . Air passes through the air cleaner, then through the air flow meter (in L-type EFI only), the throttle body, the air intake chamber, and the intake manifold, then is fed into each cylinder. In an EFI engine, releasing the accelerator pedal closes the throttle valve fully, so during idling or fast idling, air bypasses the throttle valve and is taken directly into the cylinders via the bypass passage in the throttle body or ISC valve . AIR CLEANER AIR FLOW METER (L-type EFI) THROTTLE BODY AIR VALVE and/o r ISC VALVE Air cleane r N When the coolant temperature is low, the air valve opens and air passes through it (in addition to passing through the throttle body as usual) and enters the air intake chamber. This extra air raises the idle speed to aid in engine warm-up . In engines equipped with some types of ISC valves, the above is performed not by an air valve, but by the ISC valve . Please refer to the section on the ISC system (see page 99) . AIR INTAKE CHAMBER INTAKE MANIFOLD Throttle bod y Bypass passage Idle speed adjusting screw Air valve D - TYPE EFI (engine without ISC valve ) Air flow mete r N Air intake chambe r 4 r OHP 5 2 CYLINDER S Idle speed adjusting screw (Some models only ) L -TYPE EFI ( engine with ISC valve) OHP 52 64 EFI - Air Induction Syste m 1 . THROTTLE BODY The throttle body consists of the throttle valve, which controls the intake air volume during normal engine operation, a bypass passage through which a small volume of air passes during idling, and a throttle position sensor which detects the opening angle of the throttle valve . Some throttle bodies are also equipped with a dashpot which causes the throttle valve to return gradually when it is closed or with a wax type air valve . During idling, the throttle valve is fully closed . As a result, intake air flows through the bypass passage into the air intake chamber . The engine speed during idling can be adjusted by the idle speed adjusting screw, which increases or decreases the volume of air passing through the bypass passage. (See the illustration of the wax type air valve at right . ) NOTE The idle speed adjusting screw adjusts the idle speed, just as the throttle adjusting screw does on a carburetor . In engines equipped with a stepper motor type or rotary solenoid type ISC valve, the volume of air flowing through the bypass passage is controlled by the ISC valve . Therefore, in some engines, the idle speed adjusting screw is set to the fully-closed position at the factory, while in others, an idle adjusting screw is not provided . 2 . AIR VALVE The air valve controls the engine idling speed when the engine is cold . Some engines equipped with an ISC valve do not use this air valve . (For further details on the ISC valve, see page 99 . ) WAX TYPE The wax type air valve consists of a thermo valve and a gate valve . The thermo valve is filled with thermo wax . The volume of this wax changes according to the coolant temperature. The wax type air valve utilizes these characteristics of the thermo wax to open and close the gate valve in order to control the engine idling speed . Idle speed adjusting scre w Bypass passage Coolant Throttle valve BI-METAL TYPE OHP 53 The bi-metal type air valve consists of a bi- metal element, a heat coil, and a gate valve . Current flows simultaneously to the heat coil and the fuel pump. This heats the element, causing it to change shape . This in turn causes the gate to close gradually . Heat coil (ja To air intake Bi-metal\ IP~ chamber element Gate valve From air cleaner OHP 5 3 65 EFI - Functions of Engine EC U FUNCTIONS OF ENGINE EC U The Engine ECU calculates the basic fuel injection duration in accordance with two signals : 1) the intake manifold pressure signal from the manifold pressure sensor (in D-type EFI), or the intake air volume signal from the air flow meter (in L-type EFI) ; and 2) the engine speed signal . It bases its calculations on a program stored in its memory . The Engine ECU also determines the optimum fuel injection duration for each engine condition based on signals from various other sensors . Control by the Engine ECU of the fuel pump, fuel pressure-up function, and cold start injector are covered in the section on the fuel system (See page 53), and control of the oxygen sensor heater is covered in the section on the other control systems (See page 113) . 1 . FUEL INJECTION METHODS AND INJECTION TIMING Fuel injection methods include the method in which fuel is injected by the injectors into all cylinders simultaneously, the method in which the cylinders are arranged into several groups and fuel is injected into groups of cylinders in sequence, and the method in which fuel is injected into each cylinder separately . Fuel injection timing can also differ depending on the engine model, with some engines being started at all times with a predetermined timing and other engines being started with an injection timing calculated by the ECU in accordance with the intake air volume, engine speed, etc . The basic fuel injection methods and injection timing are as follows : INJECTION METHODS INJECTION TIMING ENGINES* ' Intake stroke Ignition Fuel injection 4A-GE (D-type EFI, 1989 an d before ) 4A-FE ( en ines w/o lea n g 5 ' mixture sensor ) 3 3 S 63 1S-E, 2S-E, 3S-FE, 5S-F E SIMULTANEOU 2 t t 5M-GE, 6M-G E 4 4Y- E 0° 360° 720` 22R-E, 22R-TE Crankshaft angle OHP 54 3VZ-E, 3F-E* 2 Note : This graph shows the injection timing for the 3E-E 2E- E 6M-GE engine . , 2RZ-E, 2TZ-F E Intake stroke - Ignition Fuel injectio n ~T . 5 t 3 1G-G E 2 GROUPS 6 4A-GE ( L-type EFI ) 2 3 3 d 4 ' 4A GE (D type EFI, 1989 a n . ) f t 0° 360° 720° e r a Crankshaft angle OHP 54 4A-GZ E Note : This graph shows the injection timing for th e 1G-GE engine . 66 EFI - Functions of Engine ECU 13 INJECTION METHODS INJECTION TIMING ENGINES* ' Intake stroke Ignition Fuel injectio n 1 5 3 7M-G E 3 GROUPS 6 7M-GTE 4 i s 2VZ-FE 0° 3600 720 0 Crankshaft angle OHP 5 4 Note : This graph shows the injection timing for th e 7M-GE engine. Intake stroke Ignition Fuel injectio n 1 f 8 i i 1_ 01 1 4 i i 4 GROUPS 3 j 1UZ-F E 6 i f 5 S f 7 2 i 0° 360° 720° 1080 ° Crankshaft angle OHP 54 Intake stroke Ignition Fuel injectio n INDEPENDENT 3S-G E SEQUENTIAL) 3S-GTE ( 2 4A-FE (engines w/lean 0° 360° 720° 1080 ° Crankshaft angle OHP 54 mixture sensor ) FOR 1S-i Intake stroke i Ignition Fuel injectio n 1 t 3 4 2 t S- i 0` 360° 720° 1080 ° Crankshaft angle OHP 5 4 1 Applicable engines were manufactured in September 1991 . Refer to the respective engine Repair Manuals or Electrical Wiring Diagrams for later changes and addi- tions . 2 The fuel injection volume in the 3F-E engine is controlled separately for the front three cylinders and the rear three cylinders . However, since fuel is injected into the front and rear cylinders once each time the crankshaft turns, injection is simultaneous . ,-- NOTE There are some engines in which basic fuel injection methods and the injection method employed during starting are different . 67 ® EFI - Functions of Engine EC U 2 . FUEL INJECTION DURATION CONTRO L The actual fuel injection duration is determined by two things: 1) the basic injection duration, which is, in turn, determined by the intake air volume and the engine speed ; and 2) various corrections based on signals from the various sensors. (During engine starting [cranking], however, fuel injection duration is determined differently, because the amount of intake air i s r- Sta rting injection contro l Fuel injection duration control ' After-sta rt injection control not stable during cranking . See page 70 for more details.) Corrections differ depending on the engine model, because each respective engine has its own characteristics to take into consideration . The following table shows the main controls that make up fuel injection control : Basic injection duration control Intake air temp. correction Voltage correctio n Basic injection duration contro l Injection corrections Voltage correctio n ,,--REFERENCE Fuel injection duration control consists of syn- chronous injection, in which injection is per- formed at a predetermined crankshaft angle as described above as well as asynchronous injec- tion in which injection is performed irrespective of the crankshaft angle . Asynchronous injection consists of starting in- jection control in which injection is performed only once during cranking and acceleration in- jection in which injection is performed only once during acceleration . Synchronous F injection Fuel injection duration control Asynchronous injection Intake air temp . correction After-start enrichment Warm-up enrichment Air-fuel ratio correction during transition Power enrichment Air-fuel ratio feedback correctio n CO emission control correction Idling stability correction High-altitude compensation correctio n Fuel cut-of f Starting injection ~ contro l _After-start injection control rStarting injection contro l L Acceleration injection contro l 68 EFI - Functions of Engine EC U The relationship between fuel injection duration control and the major signals from each sensor is shown in the following table : ® REFERENCE The signals used for each type of control may differ depending on the engine model . N SIGNALS w w 0 _J a. P: z W a- CC U) 7 h HL LU _J (L M V) x v) cc ~ w D xN w w xa d = ¢~ H C7 p za ?d x u FUEL INJECTION DURATION CONTROL m Neu 0 0 U_ ( L ;o Z 0 w M N j = N a s Starting injection control 0 0 0 0 0 Basic injection For D-type EFI 0 0 duration control For L-type EFI 0 11 0 Intake air temp . correction 0 After-start enrichment 0 0 Warm-up enrichment 0 Power enrichment 0 0 0 0 Acceleratio n Air-fuel ratio enrichment 0 0 0 0 0 0 correction correctio n during Deceleratio n transition lean 0 0 0 0 0 0 After-sta rt correctio n injection control Air-fuel Oxygen 0 42 ratio senso r feedback Lean mixture 0 correction senso r CO emission contro l correction * O O Idling stability correction 0 0 High-altitude compensation 0 correction During deceleration O 0 O 0 Fuel cut-off At hig h engine 0 speeds At hig h vehicle 0 speed s Voltage correction -To- * Only engines without oxygen sensor or lean mixture sensor . 69 START INJECTION CONTROL EFI - Functions of Engine EC U During engine starting, it is difficult for the manifold pressure sensor (for D-type EFI) or the air flow meter (for L-type EFI) to accurately sense the manifold pressure or the amount of air being taken in, due to large fluctuations in engine speed. For this reason, the Engine ECU selects from its memory a basic injection duration that is suitable for the coolant temperature and engine speed, regardless of in- take manifold pressure or intake air volume . It then adds to this an intake air temperature correc- tion (See page 72) and a voltage correction (See page 79) to obtain the actual injection duration . When the weather is cold, the cold start injection system operates in order to improve startability (See page 63) . Basic injection duration during sta rtin g  THW OHP 5 5 Injection signal during startin g Low ---- On some models, injection duration increases a s N E Intake air temperature correctio n THA Voltage correction  + B 20 (68) Coolant temperature °C (°F) High OHP 55 -RELEVANT SIGNALS  Crankshaft angle (G)  Engine speed (NE )  Coolant temperature (THW)  Intake air temperature (THA)  Battery voltage (+B ) REFERENCE In some engine models, the starter (STA) signal is also used to inform the Engine ECU that the engine is being cranked . 70 EFI - Functions of Engine EC U AFTER-START INJECTION CONTRO L When the engine is running at a more-or-less steady speed above a predetermined rpm, the Engine ECU determines the injection signal duration as explained below : Injection signal duration = basic injection duration x injection correction* + voltage correctio n *Injection correction is the sum and product of various correction coefficients . Basic injection duration  VS, KS, VG or PI M  N E Injection corrections  TH W  THA  PSW or VTA  Other s Voltage correction  +B Actual injection duratio n Injection signal OHP 55 1 Basic injection duration FOR D-TYPE EF I This is the most basic injection duration, and is determined by the manifold pressure (PIM signal) and the engine speed (NE signal). The internal memory of the Engine ECU contains data on various basic injection durations for various manifold pressures and engine speeds . -RELEVANT SIGNALS  Intake manifold pressure (PIM)  Engine speed (NE ) REFERENCE Since the intake efficiency varies depending on the valve clearance, the intake air volume may vary even if the intake manifold pressure stays the same . Therefore, in D-type EFI, when the valve clearance varies, the air-fuel ratio of the air-fuel mixture will change slightly .  Since engines equipped with an oxygen sen- sor correct injection duration according to the air-fuel ratio feedback correction, the air-fuel ratio is always maintained at the op- timal level .  In engines which are not equipped with an oxygen sensor, the air-fuel ratio is adjusted by a variable resistor (See page 41) . 71 0 FOR L-TYPE EFI EFI - Functions of Engine EC U This is the most basic injection duration, and is determined by the volume of air being taken in (VS, KS or VG signal) and the engine speed (NE signal) . The basic injection duration can be ex- pressed as follows : Basic injection Intake air volume duration =K x Engine spee d where K: correction coefficient -RELEVANT SIGNAL S  Intake air volume (VS, KS or VG)  Engine speed (NE) 2 Injection corrections The Engine ECU is kept informed of engine running conditions at each moment by means of signals from various sensors. It then makes various corrections in the basic injection duration based on these signals . INTAKE AIR TEMPERATURE CORRECTIO N The density of the intake air will change depending on its temperature. For this reason, the Engine ECU must be kept accurately informed of the intake air temperature (by means of the intake air temperature sensor) so that it can adjust the injection duration to maintain the air-fuel ratio that is currently required by the engine. For this purpose, the ECU considers 20°C (68°F) to be the "standard temperature" and increases or decreases the amount of fuel injected depending upon whether the intake air temperature falls below or rises above this temperature . This correction results in an increase or decrease in the injection volume by a maximum of about 10% (for the Karman vortex type air flow meter, this is about 20%) . In case of hot-wire type air flow meters, since the air flow meter itself outputs a signal that is corrected by the intake air temperature, the in- take air temperature correction is not necessary . ,,- ivv I r- Low 20 High (68 ) Intake air temperature °C (°F ) -RELEVANT SIGNA L  Intake air temperature (THA) OHP 5 5 72 EFI - Functions of Engine EC U AFTER-START ENRICHMENT Immediately after starting (engine speed above a predetermined rpm), the Engine ECU causes an extra amount of fuel to be supplied for a predetermined period to aid in stabilizing engine operation . The initial after-start enrichment correction is determined by the coolant temperature, and the amount gradually falls thereafter at a certain constant rate . When the temperature is extremely low, this enrichment roughly doubles the injection volume . 1 .0 r ------------------------------- 0 * Low ~ (6 O A - Hig h Coolant temperature °C (°F) Depending on the engine models . -RELEVANT SIGNALS  Engine speed (NE )  Coolant temperature (THW) OHP 5 6 REFERENCE In some engine models, the starter (STA) signal is used as a condition for beginning this correction . WARM-UP ENRICHMENT ❑ Since fuel vaporization is poor when the engine is cold, the engine will run poorly if a richer fuel mixture is not supplied . For this reason, when the coolant temperature is low, the water temperature sensor so informs the Engine ECU, which increases the amount of fuel injected to compensate until the coolant temperature reaches the predetermined temperature . When the temperature is extremely low, this enrichment roughly doubles the injection volume . Low- 60" ~High (140 ) Coolant temperature °C (°F ) Depending on the engine models . -RELEVANT SIGNA L  Coolant temperature (THW) OHP 56 REFERENCE In some engine models, the amount of this enrichment changes slightly when the IDL signal goes on or off, and it also changes in accordance with the engine speed . 73 ® POWER ENRICHMENT EFI - Functions of Engine EC U When the engine is operating under a heavy load, the injection volume is increased in accordance with the load in order to ensure proper engine operation . Methods for sensing whether the engine is operating under a heavy load differ depending on the engine model . In some engines, it is determined by the throttle valve opening angle, while in other engines, it is determined by the intake air volume . This enrichment increases the injection volume by 10 to 30% . -RELEVANT SIGNAL S  Throttle position (PSW or VTA )  Intake manifold pressure ( PIM) or intake air volume (VS, KS or VG )  Engine speed (NE ) (_ REFERENCE 1 . In some engine models, the amount of increase also differs in accordance with the coolant temperature . 2 . In some engine models, when the coolant temperature is high, the fuel injection amount is increased to lower the exhaust gas temperature and to prevent the engine from overheating . 3 . In some engine models, the kick-down switch (KD) signal is used as a condition for begining this correction . AIR-FUEL RATIO CORRECTION DURING TRANSITION S A "transition" is the moment when the engine rpm changes, either during acceleration or deceleration . During a transition, the injection volume must be increased or decreased to assure proper engine pe rformance . a . Acceleration Enrichment Correctio n When the Engine ECU detects engine acceleration based on signals from the various sensors, it increases the injection volume to improve acceleration performance . The initial correction value is determined by the coolant temperature and the rate of acceleration . The amount gradually decreases from that point . b. Deceleration Lean Correctio n When the ECU detects engine deceleration, it decreases the injection volume as necessary to prevent over-rich injection during deceleration . -RELEVANT SIGNAL S  Intake manifold pressure ( PIM) or intake air volume (VS, KS or VG )  Engine speed (NE )  Vehicle speed (SPD )  Throttle position (IDL, PSW or VTA)  Coolant temperature (THW ) 74 EFI - Functions of Engine EC U AIR-FUEL RATIO FEEDBACK CORRECTIO N a. Oxygen Senso r The Engine ECU corrects the injection duration based on the signals from the oxygen sensor to keep the air-fuel ratio within a narrow range near the theoretical air-fuel ratio . (This is called a "closed-loop" operation . ) In order to prevent overheating of the catalyst and assure good engine operation, air-fuel ratio feedback does not occur under the following conditions (open-loop operation) :  During engine start in g  During after-start enrichment  During power enrichment  When the coolant temperature is below a predetermined leve l  When fuel cut-off occurs  When the lean signal continues longer than a predetermined tim e The ECU compares the voltage of the signals sent from the oxygen sensor with a predetermined voltage . If the voltage of a signal is higher than that voltage, it judges the air-fuel ratio to be richer than the theoretical air-fuel ratio and reduces, at a constant rate, the amount of fuel injected. If the voltage of a signal is lower, it judges that the air-fuel ratio is leaner than the theoretical air-fuel ratio, and increases the amount of fuel injected . The correction coefficient used by the ECU varies over a range of 0 .8 to 1 .2, and is 1 .0 during an open loop operation . High (rich) RELEVANT SIGNAL ~Oxygen sensor (OX) OHP 5 6 Two oxygen sensors are used on some models . Even if the signal of the main oxygen sensor changes over time, the air-fuel ratio can be main- tained within a narrow range near the theoretical air-fuel ratio by using a sub oxygen sensor . In addi- tion, catalyst deterioration can be also detected by comparing the signals of the two oxygen sen- sors . Catalytic converte r Decreased Increased OHP 56 Engine ECU 75 NOTE Air-fuel ratio learned control ; EFI - Functions of Engine EC U When engine condition changes over time, the air-fuel ratio that is created from basic injection duration calculated by the Engine ECU deviates from the theoretical air-fuel ratio . When this happens, time is required for the air-fuel ratio to return to the theoretical air-fuel ratio by air-fuel ratio feedback correction . The deviation may also exceeds the correction range of air-fuel ratio feedback correction . Consequently, the Engine ECU remembers the central value of the correction ratio and cor- rects the amount of deviation from the central value (a) for basic injection duration . This func- Correction ratio 1 . 2 1 .0 0.8 Lean mixture Normal conditio n b. Lean Mixture Senso r The ECU corrects the injection duration based on signals from the lean mixture sensor to keep the air-fuel ratio within the "lean" range . (This is called a "closed-loop" operation . ) In order to prevent overheating of the catalyst and assure good engine operation, air-fuel ratio feedback does not occur under the following conditions (open-loop operation) :  During engine startin g  During after-start enrichment  During power enrichmen t  When the coolant temperature is below a predetermined leve l  When fuel cut-off occurs tion is referred to as air-fuel ratio learned con- trol, and the value remembered by the Engine ECU is referred to as the learned value . As a result of this learned control, air-fuel feed- back correction is constantly able to correct the central value of the correction ratio with a value of 1 .0 . This enables the air-fuel ratio to return rapidly within a narrow range near the theoretical air- fuel ratio . Furthermore, learned control is per- formed when feedback correction is being per- formed . Central feedback valu e Over life tim e The ECU determines the target air-fuel ratio based on signals from the sensors . It then converts this ratio to an electric current and compares this current with the current from the lean mixture sensor . If the current from the lean mixture sensor is larger than the target current, it judges the air-fuel ratio to be leaner than the target air-fuel ratio and increases the amount of fuel injected . If the current from the lean mixture sensor is smaller, it judges that the air- fuel ratio is richer than the target air-fuel ratio, and reduces the amount of fuel injected . The correction coefficient used by the ECU varies over a range of 0 .8 to 1 .2, and is 1 .0 during an open-loop operation . 76 EFI - Functions of Engine EC U LS signa l Correction ratio Decreased Increased Engine ECU Large Target current Smal l OHP 57 ❑ Idle mixture adjustinc screw OHP 5 7 D-type EFI without oxygen senso r L-type EFI without oxygen sensor but with op- tical Karman vortex type air flow meter or hot-wire type air flow mete r The ECU also reduces CO emissions by controlling the injection volume in accordance with the engine speed . RELEVANT SIGNA L  Lean mixture sensor (LS) OHP 5 7 CO EMISSION CONTROL CORRECTION (D-type EFI'' and L-type EFI'z ) The injection volume can be adjusted by manually adjusting the variable resistor (See page 41) . This can be used to adjust the volume of CO emissions . RELEVANT SIGNALS  Variable resistor (VAF)  Engine speed (NE ) NOTICE It is usually not necessary to adjust the idle mixture in most models, provided that the vehicle is in good condition . However, if it does become necessa ry to do so, always use a CO meter. If a CO meter is not available, it is best not to attempt to adjust the idle mixture if at all possible . REFERENCE When the voltage of the terminal VAF is 0.1 V or less or 4 .9 V or more, the Engine ECU discon- tinues CO emission control correction . Variable resistor 77 IDLING STABILITY CORRECTION (D-type EFI only) EFI - Functions of Engine EC U The fuel injection volume is increased or decreased in accordance with changes in the engine speed in order to achieve idling stability . In order to do this, the injection volume is increased when the engine speed drops, and is decreased when it rises . RELEVANT SIGNALS  Engine speed (NE )  Thro tt le position (IDL ) REFERENCE In some engine models, engine idling is detected by the change of the intake manifold pressure (PIM) signal . HIGH-ALTITUDE COMPENSATION CORRECTION (L-type EFI with vane type air flow meter or op- tical Karman voltex type air flow meter only ) The density of oxygen in the atomosphere is lower at high altitudes . As a result, the amount of intake air flow measured by the air flow meter becomes greater than the amount of oxygen ac- tually being taken into the engine . This means that if the fuel were injected under the same condi- tions as at sea level, the air-fuel mixture would become richer . For this reason, the ECU corrects the fuel injection volume based on signals from the high- altitude compensation sensor and the air flow m ete r . This correction decreases the injection volume by about 10% at 1000 meters above sea level (for example) . 101 .3 kPa ( 760, 29.9) ( mmHg, in . Hg ) (low altitude) -Atmospheric pressure , Low altitude ) OHP 58 -RELEVANT SIGNA L  High-altitude compensation (HAC ) FUEL CUT-OF F a . Fuel Cut-Off during Deceleration During deceleration from a high engine speed with the throttle valve completely closed (idle contact on), the ECU halts injection of fuel in order to improve fuel economy and reduce undesirable emissions . When the engine speed falls below a predetermined level or the throttle valve is opened (idle contact off), fuel injection is resumed . The fuel cut-off engine speed and the fuel injection resumption engine speed are high when the coolant temperature is low . There are also some engine models in which these engine speeds drop during braking (i .e ., when the stop lamp switch is on) . 2,000 Low- Coolant temperature- High OHP 58 78 EFI - Functions of Engine EC U -RELEVANT SIGNALS  Throttle position (IDL)  Engine speed (NE )  Coolant temperature (THW)  Stop lamp switch (STP ) - REFERENCE 1 . In some manual transmission models, the clutch switch (N/C) signal is also used as a condition for fuel cut-off . 2 . There are some models in which the fuel will be cut off when the injection volume during deceleration falls below the predeter- mined level even if the throttle valve is not completely closed (idle contact off) . i b . Fuel Cut-Off at High Engine Speed s To prevent engine over-run, fuel injection is halted if the engine speed rises above a predetermined level . Fuel injection is resumed when the engine speed falls below this level . RELEVANT SIGNA L  Engine speed (NE ) c. Fuel Cut-Off at High Vehicle Speed s In some vehicles, fuel injection is halted if the vehicle's speed exceeds a predetermined level . Fuel injection resumes after the speed drops below a predetermined level . - RELEVANT SIGNAL  Vehicle speed (SPD ) IYV I C The Engine ECU also performs various other corrections in addition to these (page 72 to 79) . 3 Voltage correctio n There is a slight delay between the time that the Engine ECU sends an injection signal to the injectors and the time that the injectors actually open. This delay becomes longer the more the voltage of the battery drops . This means that the length of time that the injector valves remain open would become shorter than that calculated by the ECU, causing the actual air- fuel ratio to become higher (i .e., leaner) than that required by the engine, if this were not prevented by voltage correction . In voltage correction, the ECU compensates for this delay by lengthening the duration of the injection signal by a period corresponding to the length of the delay . This corrects the actual injection period so that it corresponds with that calculated by the ECU . (The amount of this correction value depends on the engine model . ) Voltage correctio n Off Ope n Closed Injector actually open OHP 6 8 0 I ---------------------------- Standard operating delay tim e Low- 14- High Batt ery voltage (V) OHP 58 RELEVANT SIGNA L  Battery voltage (+B) Injection signa l ~ 79 l-6 L OW3W ESA - Genera l ESA (ELECTRONIC SPARK ADVANCE ) GENERAL ® The ESA (electronic spark advance) system is a mechanical advancer) controls the ignition system in which an ECU (rather than a timing of the ignition system . Igniter Ignition coi l OHP 59 BASIC CONSTRUCTION OF ES A 1 . IGNITION TIMING AND ENGINE RUNNING CONDITION S In order to maximize engine output efficiency, the air-fuel mixture must be ignited when the maximum combustion pressure occurs ; that is, at about 10° after TDC (top dead center) . However, the time from ignition of the air-fuel mixture to the development of maximum combustion pressure varies depending on the engine speed and the manifold pressure ; ignition must occur earlier when the engine speed is higher and later when it is lower . In con- ventional EFI, the timing is advanced retarded by a governor advancer in distributor . Furthermore, ignition must also be advanced when the manifold pressure is low (i .e ., when there is a strong vacuum) . In conventional EFI, this is achieved by the vacuum advancer in the distributor . However, optimal ignition timing is also affected by a number of other factors besides engine speed and intake air volume, such as the shape of the combustion chamber, the temperature inside the combustion chamber, etc . For this reason, governor and vacuum advancers cannot provide ideal ignition timing for the engine . In the ESA system, the engine is provided with nearly ideal ignition timing characteristics . The ESA works as follows: the ECU determines ignition timing from its internal memory, which contains the optimal ignition timing data for each engine running condition, then sends the appropriate ignition timing signal to the igniter . Since the ESA always ensures optimal ignition timing, both fuel efficiency and engine power output are maintained at optimal levels . and the 80 ® ESA - Genera l 2 . IGNITION TIMING AND GASOLINE QUALITY ESA Governor advance r Engine speed - Hig h ADVANCING BY ENGINE SPEE D Ideal ignitio n Manifold vacuum - Hig h VACUUM ADVANCIN G timing I ESA OHP 59 Vacuum advancer OHP 59 In some engine models, two ignition timing advance patterns, according to the fuel octane rating ( premium or regular), are stored in the ECU . The ignition timing can be changed to match the gasoline being used (premium or regular) by operating the fuel control switch or connector (See page 40) . In some engine models, this is done automatically by the Engine ECU's fuel octane judgement fun- ction (See page 116) . 81 ESA - Genera l The following table shows the specifications for the 4A-FE engine. Items marked with circles in the "APPENDIX" column are included in the specifications for each engine in the APPENDIX section (page 188) in the back of this manual . In addition, for those items with circle in the "STEP 2 (IGNITION)" column in the following table, refer to the Step 2, vol . 3 (Ignition System) manual for a detailed explanation of the relevant items . ESA (ELECTRONIC SPARK ADVANCE) PAG E (THIS ITEM REMARK APPENDIX STEP 2 MANUAL) (IGNITION ) Crankshaft angle ( initial ignition timing 83 ~ ) angle) judgement ` IGT (ignition timing) signal 83 0 IGF (ignition confirmationl signal 84 0 Conventional ignition circuitry 85 0 for TCC S Ignitio n i i DLI (distributorless ignition) 86 rcu tr y c system DIS (direct ignition system) 88 Starting ignition control 91 ) Basic ignition advance angle 9 2 Warm-up correction 93 0 Over-temperature correction 9 3 Stable idling correction 94 0 EGR correction 94 0 With EG R 0 Air-fuel ratio feedback 95 With oxygen sensor w correctio n (D Knocking correction 95 With knock senso r C Torque control correction 9 6 0 Transition correction 97 ~ N C Cruise control correction 9 7 .~ " C a) U Traction control 9 7 LL correctio n ACIS (acoustic control 0 a) induction system) 9 7 correctio n Intercooler failure 9 7 correctio n Maximum and minimum 97 ~ advance angle contro l Ignition timing adjustment 98 ~ "Specifications for Corolla 4A-FE engine (Apr ., 1992) 82 W Point A, ' CRANKSHAFT ANGLE (INITIAL IGNITION TIMING ANGLE) JUDGEMENT The ECU judges that the crankshaft has reached 5°, 7° or 10° BTDC (depending on the engine model) when it receives the first NE signal (point iB) in the illustration below) following a G signal (point This angle is known as the "initial ignition timing angle" . TIMING ROTOR POINT A . POINT B ' G signa l G SIGNA L TIMING ROTO R AND G PICKU P COI L ------------------- ----- 5',7' or 10° BTD C TDC-.4 NE SIGNAL -N E TIMING ROTO R AND NE PICKUP l COIL OHP 60 Point (B ; ) NE ESA - Crankshaft Angle ( Initial Ignition Timing Angle) Judgement, IGT Signa l 5 0 , 7° or 100 BTDC ,, ,Ignitio n r A , i I -J IGT (IGNITION TIMING) SIGNAL IGT ~ -J `---~ IGT with initial ignition timing IGT with timing advanced OHP 60 The Engine ECU sends an IGT signal to the igniter based on signals from each sensor so as to achieve the optimal ignition timing . This IGT signal goes on just before the ignition timing calculated by the microprocessor, then goes off. The spark plug fires at the point when this signal goes off. TDC TDC TDC r~ Ignition -r-k i IGTJ~ 180° (4 cylinders) 120° (6 cylinders) Ignition ~-f V TDC IGT Advance angle T Initial ingnition timing 5°, 7° or 10° BTD C (depending on engine model) OHP 6 1 83 ESA - IGF Signa l IGF (IGNITION CONFIRMATION) SIGNAL 7 4 The counter-electromotive force that is whether ignition actually occurred or not . generated when the primary current is This signal is used for diagnosis (See page 131) interrupted causes this circuit to send an IGF and the fail-safe function (See page 145) . signal to the ECU, which detects by this signa l Ignitio n coi l Ignition switch Battery IGF signal II generation circui t 0 a IGT -~ 2 Ignition .. r rnntrnl circuit II h I I N ~ I- > OHP 6 1 ~ NOTE In some recent models, the IGF signal is generated according to the primary current value . In these models, IGF is switched on when IGT is on, and IGF is switched off when the primary current exceeds the predetermined value . FOR RECENT MODEL S ON IGT OF F Primary ------~ - current 0 IGF O N OFF IGF -► FOR PREVIOUS MODEL S IGT ON OFF ~ I * Primary 12 V voltage 0 ON IGF OF F * The counter-electromotive forc e Igniter Engine ECU 84 IGNITION CIRCUITRY ESA - Ignition Circuitry The operation of the ignition system in TCCS is The types of ignition system in TCCS can be dif- basically the same as the operation of the ferentiated by the method used to distribute cur- ignition system in conventional EFI, except that rent to the spark plugs : either the conventional the igniter in the latter is turned on and off type, in which a distributor is used, or DLI directly by the signal generator . (distributorless ignition) and DIS (direct ignitio n Signal generator Distributor Ignition Igniter coi l CONVENTIONAL EFI Spark plug s OHP 6 2 In the TCCS, the signals from the signal generator first pass through the ECU befor e going to the igniter . Signal Spark generator Distributor plug s Ignition , . I Igniter coi l ~ ~ _Vv IGT TCCS ECU OHP 62 system), in which no distributor is used . In this section, we will explain the operation of both the conventional ignition system used in TCCS, and the DLI and DIS . For an explanation of the operation of the ignition system for the con- ventional EFI, refer to Step 2, vol .3 (Ignition System) . REFERENCE An igniter is included in the Engine ECU of the 4A-FE engine made by Bosch . 1 . CONVENTIONAL IGNITION CIRCUITRY FOR TCC S The microprocessor in the ECU determines the ignition timing based on the G(G1 and G2) and NE signals, as well as on signals from each sensor. After determining the ignition timing, the ECU sends an IGT signal to the igniter . When the IGT signal goes off, transistor Tr2 in the igniter goes off . As a result, the primary current to the ignition coil is interrupted, causing a high voltage (of approx . 20 to 35 kV) to be generated by the secondary coil in the ignition coil. This in turn causes sparks to be generated by the spark plugs . The igniter incorporates the following circuitry in order to deliver a stable secondary voltage and assure system reliability : ESA - Ignition Circuitry DWELL ANGLE CONTROL CIRCUIT This circuit controls the length of time during which Tr2 is on, in order to assure the proper secondary voltage . /-- IYV I C A dwell angle control circuit is provided in the Engine ECU in recent engines . The igniter starts the flow of primary current when the IGT signal is on and stops that current when it is off . The Engine ECU lengthens the dwell angle by advan- cing the timing by which the IGT signal is switched on when engine speed increases . IGF SIGNAL GENERATION CIRCUIT ® This circuit generates the IGF signal and sends it to the ECU . LOCK-UP PREVENTION CIRCUIT This circuit forces Tr2 to go off if it locks up (that is, if current flows continuously for a period longer than a predetermined period), in order to protect the ignition coil and Tr2 . OVER-VOLTAGE PREVENTION CIRCUIT This circuit forces Tr2 to go off if the power supply voltage becomes too high, in order to protect Tr2 and the ignition coil . Ignition coil\ Ignition switc h Battery Ilk Micro- processor Input circuit Senso r G NE OHP 6 2 85 ESA - Ignition Circuitry 2 . DLI (DISTRIBUTORLESS IGNITION) SYSTE M DLI is an electronic spark distribution system which distributes high voltages directly from the ignition coils to the spark plugs without the need of a conventional distributor . It differs from the conventional type of ignition system as shown below : Spark Distributor plug s ECU DLI SYSTE M Ignition coils Ignition switc h Battery OHP 63 Drive circu i Drive circuit Drive circuit OHP 63 CONVENTIONAL IGNITION CIRCUITRY FOR TCC S Engine EC U Input circuit Dwell angle control circuit Y V V ~ a OHP 63 In the DLI, the igniter is connected to the Engine ECU as shown in the figure above . There are three ignition coils: one for cylinders No . 1 and No . 6, one for cylinders No. 2 and No. 5, and one for cylinders No . 3 and No . 4. The ECU sends cylinder identification signals (IGDA and IGDB) and the IGT signal to the igniter in accordance with the G 1, G2 and NE signals from the cam posi- Igniter tion sensor which detects the crankshaft angle, engine speed and various sensors . The igniter distributes the primary current to the three ignition coils based on these signals . For this reason, the spark plugs in cylinders No . 1 and No . 6 fire simultaneously, as do those in cylinders No. 2 and No. 5 and cylinders No. 3 and No. 4. In other words, each spark plug is ignited two times in one cycle . 86 ESA - Ignition Circuitry Since the IGT signal from the ECU must be distributed to three coils, the ECU outputs two cylinder identification signals (IGDA and IGDB) . The timing of each signal is shown in the chart below . The microprocessor is informed of when cylinder No. 1 is at 100 BTDC by the next NE signal following the G2 signal, and outputs the IGDA and IGDB signals stored in memory in the combination that corresponds to the order in which the cylinders are fired, as shown in the table to the right above . The cylinder identification circuit in the igniter distributes the IGT signal to the transistor drive circuit that is connected to the relevant ignition coil, based on the combination of these signals . Switching of the IGDA and IGDB signals from 1 to 0 and from 0 to 1 is synchronized with the IGT signal . Other circuits are the same as those in the igniter for the conventional type . 3600 CA 720° CA G1 G2 No. 1 BTDC 10' (compression) 0 SIGNALS CYLINDERS IGDA IGDB No . 1 and No. 6 0 1 No. 5 and No . 2 0 0 No. 3 and No. 4 1 0 OHP 6 4 /-IVV 1 C High-voltage Diod e On some models, since the ignition coils have high-voltage diodes built into the secondary side, judgment of the continuity cannot be con- firmed by using an ordinary ohmmeter . To spar k plugs From + B L To igniter u High-voltage diod e No . 1 ignition No . 5 ignition No . 3 ignition No. 6 ignitio n IGT ,0 I r OHP 64 87 3 . DIS (DIRECT IGNITION SYSTEM) ESA - Ignition Circuitry Similar to DLI, DIS is the system to distribute the high voltage directly to the spark plugs from ignition coils without using a distributor . There are various types of current DIS systems, including those in which an igni- tion coil is provided for each cylinder and those in which an ignition coil is provided for every two cylinders (See Step 2, Vol . 3, "Ignition System") . The electrical circuitry shown here is for the type in which an igni- tion coil is provided for each cylinder . Igniter Engine ECU Constant voltage circuit Ignition switc h Battery I i i Spark Ignition plugs coils U U a) > ~ GT GT IGT z GT o Lock prevention circui t Constan current control circuit Dwell angle control Circui t Ignition delecting circuit F-I TACH, lGF signal outpu circuit O TACH 2JZ-GTE ENGINE (May, 1993) Control by the Engine ECU is basically the sam e as that of an ordinary ESA . The difference is tha t the Engine ECU has the same number of IGT IGT, ON OFF ~ signals as the number of ignition coils. IGT signals O N are then sent to the igniter according to the igni- IGT5 OF F tion sequence . IGT 3 IGT 6 IGT 2 IGT4 ON OF F ON OF F ON OFF ON OF F IGF* ON OFF 0 m m m U 0 a N E Sensors l *The IGF signals in DIS is normally HI (ON) , and turns to LO (OFF) during ignition . IGF 88 ESA - Functions of Engine EC U FUNCTIONS OF ENGINE ECU 1 . IGNITION TIMING CONTRO L Ignition timing control consists of two basic controls :  Sta rting ignition contro l When the engine is cranking, ignition occurs at a certain fixed crankshaft angle, regardless of engine operating conditions. This is called "initial ignition timing angle" . Initial ignition timing angl e OHP 65 Initial ignition timing angl e !4 01 Actual ignition timing OHP 6 5 REFERENCE Note that, in after-start ignition control, each type of correction differs depending on the engine model . Ignition timing control Starting ignition control Initial ignition timing angl e Initial ignition timing angle Basic ignition advance angl e After-sta rt ignition control  After-start ignition contro l Various corrections are added to the initial ignition timing angle and the basic ignition advance angle during normal operation . Corrective ignition advance control Warm-up correction Over-temp. correction Stable idling correction EGR correction Air-fuel ratio feedback correction Knocking correction Torque control correction Other correction Maximum and minimum advance angle control 89 ESA - Functions of Engine EC U The relationship between the major controls the REFERENC E make up ignition timing control and the major The signals used for certain controls may signals from each sensor is shown in the differ depending on the engine . following table . LL W W 0 J x U SIGNALS o d J P: (D 0 ~ U) LU ~ Se O O ~ > ZD (L LL Cn ¢ (n U) _j O ~V 0 Z ~ LL Q"' Z ga z _J z ~ z ~ a OW (D H! ~ O Q ~ ~ Za Z 0 j ~ u.O IGNITION TIMING CONTROL Y O Q F ~ m a ~> _J > C7 Z = CL a Z > O V) O ~ 0 Starting ignition control 0 0 Basic ignition advance angle 0 0 0 0 0 ~ C Warm-up correction 0 0 0 ~ Over-temperature correction 0 M C Stable idling correction 0 0 0 0 Y E EGR correction 0 0 0 0 0 t m _ ~ > Air-fuel ratio feedback correction 0 0 0 m ° Knocking correction 0 r o o U c~ Torque control correction* 0 0 0 0 Torque control correction also uses the vehicle speed (SP2) signal . This signal is used to control the ECT . For further details, see Step 3, vol . 4 (ECT) . 90 ESA - Functions of Engine ECU STARTING IGNITION CONTRO L Starting ignition control is carried out once immediately after input of the NE signal following the G(G1 or G2) signal . This ignition timing is called "initial ignition timing angle" . For further details, see page 83 . During sta rting, when the engine speed is still below a specified rpm (usually around 500 rpm), since the intake manifold pressure (PIM) signal or the intake air volume (VS, KS or VG) signal is unstable, the ignition timing is fixed at the initial ig- nition timing (which differs depending on the engine model) . This initial ignition timing is set directly by the back-up IC in the Engine ECU . F RELEVANT SIGNALS Crankshaft angle (G) Engine speed (NE ) REFERENCE In some engine models, the starter (STA) signal is also used to inform the ECU that the engine is being cranked . Engine EC U NE '"""" Initial ignition timing angle l signal generation circuit 11 AFTER-START IGNITION CONTRO L After-start ignition control is carried out during normal operation . The various corrections (which are based on signals from the relevant sensors) are added to the initial ignition timing angle and to the basic ignition advance angle (which is determined by the intake manifold pressure signal or the intake air volume signal, and by engine speed signal) : Ignition timing = initial ignition timing angle + basic ignition advance angl e + corrective ignition advance angle During normal operation of after-start ignition control, the ignition timing (IGT) signal calculated by the microprocessor is output through the back-up IC . Engine ECU OHP 65 IGT JUL OHP 65 91 T Basic ignition advance angle ESA - Functions of Engine EC U The basic ignition advance angle in the ESA system corresponds to the vacuum advance and governor advance angles in conventional EFI . Data on the optimal basic ignition advance angle (which correspond to the engine speed and intake manifold pressure or intake air volume) are held in the memory of the Engine ECU . IDLE CONTACT CLOSED (ON ) The ignition timing is advanced in accordance with the engine speed when the idle contact closes . om C C ~ U C - f0 > CO c o m Low- Engine speed -RELEVANT SIGNALS  Thrott le position (IDL)  Engine speed (NE) High OHP 6 6 REFERENCE In some engine models, the basic ignition ad- vance angle changes (as shown by the dotted line in the graph above) depending on whether the air conditioner is on or off . In addition, there are also models in which the advance angle is "0" at the time of the stan- dard idle speed . \1 i IDLE CONTACT OPEN (OFF ) The Engine ECU determines the basic ignition advance angle based on data stored in its memory, and based on the intake manifold pressure (or the intake air volume) and engine speed . In some engine models, two types of basic ignition advance angle data are stored in memory. One or the other of these two sets of data is then used, depending on the fuel octane rating (premium or regular) . The driver can select the data to be used by setting the fuel control switch or connector to match the octane rating of the gasoline used . In vehicles equipped with the fuel octane judgment capability, the relevant data are accessed automatically in accordance with the knock (KNK) signal from the knock sensor (Se e page 116) . RELEVANT SIGNALS  Intake manifold pressure (PIM) or intake air volume (VS, KS or VG )  Engine speed (NE )  Throttle position (IDL )  Fuel control switch or connector (R-P )  Engine knocking (KNK) J 92 ESA - Functions of Engine ECU 4 W ~2 Corrective ignition advance contro l WARM-UP CORRECTIO N The ignition timing is advanced to improve drivability when the coolant temperature is low . In some engine models, this correction changes the advance angle in accordance with the intake manifold pressure or the intake air volume . The ignition timing angle is advanced by approximately 15° by this correction during extremely cold weather . OVER-TEMPERATURE CORRECTIO N To prevent knocking and overheating, the ignition timing is retarded when the coolant temperature is extremely high . The ignition timing angle is retarded a maximum of approximately 5° by this correction . 0 -5 110* (230) Coolant temperature °C ('F ) *Depending on the engine models . 60* (140 ) Coolant temperature 'C ('F) *Depending on the engine models . OHP 66 -RELEVANT SIGNAL S  Coolant temperature (THW )  Intake manifold pressure (PIM) or intake air volume (VS, KS or VG ) REFERENCE In some engine models, the throttle position (IDL) signal or the engine speed ( NE) signal is used as the relevant signal for this correction . RELEVANT SIGNAL Coolant temperature (THW) OHP 66 REFERENCE In some engine models, the following signals are also used for this correction .  Intake manifold pressure ( PIM) signal or intake air volume (VS, KS or VG) signa l  Engine speed ( NE) signa l  Throttle position (IDL) signal etc . 93 ESA - Functions of Engine EC U STABLE IDLING CORRECTIO N When the engine speed during idling has fluc- tuated from the target idle speed, the Engine ECU adjusts the ignition timing to stabilize the engine speed . The ECU is constantly calculating the average engine speed. If the engine speed falls below the target speed, the ECU advances the ignition timing by a predetermined angle . If the engine speed rises above the target speed, the ECU retards the ignition timing by a predetermined angle. The ignition timing angle is changed a maximum of approximately ±5° by this correction . This correction is not executed when the engine exceeds a predetermined speed . O f_ Difference from target idle speed OHP 66 -RELEVANT SIGNALS  Engine speed (NE )  Throttle position (IDL)  Vehicle speed (SPD ) REFERENCE 1 . In some engine models, the advance angl e changes depending on whether the air conditioner is on or off . 2 . In some engine models, this correction only operates when the engine speed is below the target engine speed . EGR CORRECTIO N When the EGR is operating and the IDL contact is off, the ignition timing is advanced according to the volume of the intake air and the engine speed to improve drivability. -RELEVANT SIGNAL S  Intake manifold pressure ( PIM) or intake air volume (VS, KS or VG )  Engine speed (NE )  Throttle position (IDL and PSW or VTA ) 94 ESA - Functions of Engine EC U AIR-FUEL RATIO FEEDBACK CORRECTION (engines with oxygen sensor ) During air-fuel ratio feedback correction, the engine speed varies according to the increase or decrease in the fuel injection volume . The engine is especially sensitive to changes in the air-fuel ratio when it is idling, so stable idling is ensured by advancing the ignition timing at this time in order to match the fuel injection volume of air-fuel ratio feedback correction . The ignition timing angle is advanced a maximum of approximately 5° by this correction . This correction is not executed while the vehicle is being driven . -RELEVANT SIGNALS  Oxygen sensor (OX)  Throttle position (IDL)  Vehicle speed (SPD) KNOCKING CORRECTION a If engine knocking occurs, the knock sensor converts the vibrations created by the knocking into voltage signals and sends them to the Engine ECU . Distributo r Spark plug Igniter & coi l Sensor Engine EC U w Engine knocking correctio n circuitry OHP 6 7 The ECU judges whether the strength of the knocking is at one of three levels, strong, medium or weak, according to the strength of the KNK signals, and changes the corrective ignition retard angle accordingly . In other words, if the knocking is strong, the ignition timing is retarded a lot, while if knocking is Weak, it is retarded only a li ttle . When engine knocking stops, the ECU stops retarding and begins advancing the ignition timing by fixed angles a little at a time . This ignition timing advance continues until engine knocking recurs, at which point the ignition timing is again retarded . The ignition timing angle is retarded a maximum of approximately 10° by this correction . Retarding of the ignition timing during knocking is carried out within the knocking correction range . In some engines, this means when the engine is operating under a heavy load (vacuum below approx. 26.7 kPa [200 mmHg, 7 .9 in .Hg]), while in other engines, it covers vi rtually the full engine load range . 95 ESA - Functions of Engine EC U The ECU feeds back signals from the knock TORQUE CONTROL CORRECTIO N sensor to correct the ignition timing as shown below. ENGINE KNOCKING OCCUR S TIMING ADVANCED TIMING RETARDED ENGINE KNOCKING STOPS OHP 6 7 Weak Engine knocking Strong OHP 6 7 -RELEVANT SIGNAL -  Engine knocking (KNK) In the case of vehicles equipped with the ECT (electronically-controlled transmission), each clutch and brake in the planetary gear unit of the transmission or transaxle generates shock to some extent during shifting. In some models, this shock is minimized by delaying the ignition timing when gears are up- or down-shifted . When gear shifting starts, the Engine ECU retards the engine ignition timing to reduce the engine torque . As a result, the shock of engagement of the clutches and brakes of the planetary gear unit is reduced and the gear shift change is performed smoothly . The ignition timing angle is retarded a maximum of approximately 200 by this correction . This correction is not performed when the coolant temperature or battery voltage is below a predetermined level . -RELEVANT SIGNALS  Engine speed (NE )  Throttle position (VTA )  Coolant temperature (THW)  Ba ttery voltage (+B ) 96 ESA - Functions of Engine EC U OTHER CORRECTIONS Engines have been developed with the following corrections added to the ESA system (in addition to the various corrections explained so far), in order to adjust the ignition timing with extremely fine precision . a . Transition Correctio n During the transition (change) from deceleration to acceleration, the ignition timing is either advanced or retarded temporarily in accordance with the acceleration . b . Cruise Control Correction When driving downhill under cruise control, in order to provide smooth cruise control operation and minimize changes in engine torque caused by fuel cut-off due to engine braking, a signal is sent from the Cruise Control ECU to the Engine ECU to retard the ignition timing . c. Traction Control Correctio n This retards the ignition timing, thus lowering the torque output by the engine, when the coolant temperature is above a predetermined temperature and the traction control system is operating . d . ACIS (Acoustic Control Induction System) Correctio n When the engine speed rises above a predetermined level, the ACIS operates. At that time, the Engine ECU advances the ignition timing simultaneously, thus improving output . See page 120 for details on the ACIS . e. Intercooler Failure Correctio n This correction retards the ignition timing if the intercooler fail signal goes on . MAXIMUM AND MINIMUM ADVANCE ANGLE CONTRO L If the ignition timing (initial ignition timing + basic ignition advance angle + corrective ignition advance angle) becomes abnormal, engine operation will be adversely affected . To prevent this, the Engine ECU controls the actual ignition angle (ignition timing) so that the sum of the basic ignition advance angle and corrective ignition advance angle cannot be greater or less than certain values . These values are : MAX. ADVANCE ANGLE 350 -45 0 MIN . ADVANCE ANGLE -10° - 0 ° Advance angle = Basic ignition advance angl e + corrective ignition advance angle 97 ESA - Functions of Engine EC U 2 . IGNITION TIMING ADJUSTMENT The angle to which the ignition timing is set during ignition timing adjustment is called the "standard ignition timing ." It consists of the initial ignition timing (See page 83), plus a fixed ignition advance angle (a value that is stored in the ECU and output during timing adjustment regardless of the corrections, etc ., that are used during normal vehicle operation) . Initial ignition timing angl e Fixed ignition advance angle Standard ignition timing angle OHP 68 Ignition timing adjustment is carried out as follows : 1) Set the standard ignition timing by connecting terminal Ti (or TEi) of the check connector or TDCL with terminal Ei, with the idle contacts on . This will cause the standard ignition timing signal to be output from the back-up IC in the same way as during after- start ignition control (See page 91) . Check connector TorTE1 El TDCL OHP 68 SST El TE1 OHP 68 The standard ignition timing differs depending on the engine model, as shown in the following table . When tuning up the engine, refer to the repair manual for the relevant engine . FIXED ENGINE INITIAL IGNITION STANDAR D IGNITION IGNITIO N MODEL ADVANC E TIMING TIMIN G ANGLE Type 1 100 BTDC 0° BTDC 100 BTDC Type 2 5° BTDC 50 BTDC 10° BTDC Type 3 70 BTDC 0° BTDC 7° BTDC OHP 6 8 2) If the standard ignition timing is not as specified above, adjust it . /.-- NOTE 1 . Even if terminal T1 or TE1 and terminal E1 are connected, the ignition timing will not be fixed at the standard ignition timing unless the idle contacts are on . 2. Since the G and NE signal generators are fix- ed in recent models, there are cases in which ignition timing cannot be adjusted . 98 ISC - Genera l ISC (IDLE SPEED CONTROL ) GENERAL The ISC system controls the idle speed by means of the ISC valve to change the volume of air flowing through the throttle valve bypass in accordance with signals from the ECU . There are four types of ISC valve, as follows :  Stepper motor typ e  Rota ry solenoid type  Duty-control ACV (air control valve) type  On-off control VSV (vacuum switching valve) type Air cleaner Ir i Ignition switc h Battery I i ~ Engine ECU Sensors BASIC CONSTRUCTION OF ISC ® The control functions in the ISC system differ depending on the engine. The power steering idle-up mechanism is controlled by a separate idle-up device (see Step 2, vol. 11 ["Steering System"] for more details) . Since the volume of air passed through the duty- control ACV type ISC valve and the on-off control VSV type ISC valve is small, a separate air valve for controlling the greater amount of air needed during cold starting is also provided . See page 65 for details on this air valve . OHP 69 99 ® ISC - Genera l The following table shows the specifications for specifications for each engine in the APPENDIX the 4A-FE engine . Items with circles in the section (page 188) at the back of this manual . "APPENDIX" column are included in th e PAG E ISC (IDLE SPEED CONTROL) (THIS ITEM REMARK APPENDIX MANUAL ) Stepper motor type 10 1 Rotary solenoid type 102 ISC valve Duty-control ACV type 104 On-Off control VSV type 104 Starting set-up 10 5 After-start control 106 Warm-up (fast-idle) control 106 Stepper Feedback control 107 motor type ISC valve Engine speed change 10 7 estimate contro l Electrical load idle-up 10 7 contro l Other controls 10 7 Starting control 108 ~ Warm-up (fast-idle) 108 o Rotary contro l solenoid Feedback control 108 L 7 type IS C valve Engine speed change 109 estimate contro l Other controls 109 Starting control 11 0 Duty-control Feedback control 11 0 ACV type Engine speed change 1 1 0 ISC valve estimate contro l Constant duty control 11 0 On-off control VSV type ISC valve 11 1 *Specifications for Carolla AE101 4A-FE engine (Apr ., 1992 ) 100 ISC - ISC Valve ISC VALVE 1 . STEPPER MOTOR TYPE The ISC valve is mounted on the air intake chamber or throttle body. In order to control the speed at which the engine idles, it increases or decreases (based upon signals from the Engine ECU) the amount of intake air that is allowed to bypass the throttle valve . The idle speed adjusting screw* is set to the fully closed position at the factory, because the idle speed is controlled by the ISC valve . The use of the idle speed adjusting screw has been discontinued in recent models . Air flow meter Idle speed adjusting screw * Engine ECU ISC valve Thro tt le valv e To cylinder s OHP 7 0 CONSTRUCTIO N A stepper motor is built into the ISC valve. This motor rotates the rotor clockwise or counterclockwise, moving the valve in or out . This in turn increases or decreases the clearance between the valve and valve seat, regulating the amount of air that is allowed to pass through . The ISC valve has 125 steps from the fully closed to the fully open position . Since the air flow capacity of the stepper motor type ISC valve is large, it is also used for controlling fast idle. It is not necessary to use it in combination with an air valve . Roto r Stator ® To air intake ♦ chamber Valve sea t Valve shaf t Stopper plat e OHP 70 i t From air flow mete r Small- Number of steps- Large OHP 7 0  Rotor . . . constructed of a 16-pole perma- nent magnet . (The number of poles differs depending on the engine . )  Stator . . . two sets of 16-pole cores, each of which is staggered by half a pitch in relation to the other . Two coils are wound around each core, each coil being wound in opposite directions . (The number of poles differs depending on the engine . ) OHP 7 0 OPERATIO N Current flows through one of the four coils of the stator in turn in accordance with the output from the ECU . The flow of current in coil S1 is as shown in the following illustration : 101 © S1 131 S3 S2 B2 S4 Coils Stato r Pole pa ttern of stator N MOVEMENT OF VALVE ISC - ISC Valv e I 1 OHP 7 1 The valve shaft is screwed into the rotor. The shaft is prevented from turning by means of a stopper plate, so it moves in and out as the rotor rotates. This controls the clearance between the valve and valve seat, decreasing or increasing it to regulate the amount of air allowed through the bypass . ROTATION OF ROTO R The direction of rotation of the rotor is reversed by changing the order in which current is allowed to pass through the four coils . If the stator and rotor are the 16-pole type, the rotor is rotated about 11° (1/32 of a revolution) each time current passes through the coils . When the rotor rotates one step, the positional relationship shown in the figure below develops, and the stator coils become excited . Since the N poles tend to be attracted to the S poles in the stator and rotor, and since like poles in the stator and rotor tend to repel each other, the rotor rotates one step . Stato r Rotor V ..(_C.!!!_!' Stato r Rotor 102 N 1 I N S s S 1 1 S N N S N N ~- 1/32 revolutio n s _L > Repulsion t* Attraction S S N S OHP 71 2. ROTARY SOLENOID TYPE The ISC valve is mounted on the throttle body, and intake air that bypasses the throttle valve passes through it . The ISC valve is operated by signals from the Engine ECU, and controls the amount of intake air that is allowed to bypass the throttle valve . Although older models still had an idle speed ad- justing screw, its use has been discontinued in re- cent models . Air intak e Throttle valve chambe r To cylinder OHP 7 2 The ISC valve is a small, lightweight rotary solenoid type valve . Since the air flow capacity of the rotary solenoid type ISC valve is high, it is also used for controlling fast idle . It is not necessary to use it in combination with an air valve . ISC - ISC Valve Bypass air passag e A' OHP 7 2 From To air intake air cleaner chambe r ~ L~ ;~ Bypass po rt O ~ Valve up ✓alv e Cross-section A-A' OHP 7 2  Permanent magnet Located at the end of the valve shaft, the cylindrical permanent magnet rotates when its two poles are repelled by the magnetism exe rted by coils Ti and T2 .  Valve Anchored to the midsection of the valve shaft, the valve controls the amount of air passing through the bypass port, revolving on the shaft together with the permanent magnet . ®  Coils (Ti and T2 ) Opposing each other and surrounding the permanent magnet, the two coils act as electromagnets that exert north-polarity magnetic force on the sides facing the permanent magnet when the ECU generates a duty signal . The ECU thus causes the permanent magnet to rotate, controlling the magnetic intensity of the field produced by the coils .  Bimetallic strip assembl y The bimetallic strip, similar to the one found in a regular carburetor assembly, detects changes in coolant temperature via the valve body . The guard attached to one end of the bimetallic strip senses the position of the valve shaft lever running through the notch in the guard : the lever will not trigger bimetallic strip operation as long as the ISC system is operating normally, i .e ., as long as the bimetallic strip does not contact the notched section on the guard . This mechanism acts as a fail-safe device that prevents the engine from running at excessively high or low speeds due to a defect in the ISC system's electrical circuitry . Coil T2 Valve shaf t ' Bimetal strip OHP 7 2 103 a NOTE - Duty Ratio ISC - ISC Valv e The "duty ratio" is the ratio of the interval during which current flows to the interval during which current does not flow in one cycle of a signal . The figure below shows the time in one cycle during which current flows and does not flow . A: Current flows (on ) B: Current does not flow (off ) (On ) 1 0 (Off) B Duty ratio (% ) = A+AB x 100 1 cycl e LOW DUTY RATIO HIGH DUTY RATIO (On) (On) 1 n n n 1 0 ~ (Off) ~ 0 J U u U (Off) OHP 7 3 3 . DUTY-CONTROL ACV TYP E The construction of this type of ISC valve is as shown in the following figure . While current flows according to signals from the Engine ECU, the coil becomes excited and the valve moves . This changes the gap between the solenoid valve and the valve body, controlling the idle speed. (Note, however, that the fast-idle speed is controlled using an air valve . ) From air cleaner ♦ ♦ To air intake chambe r OHP 73 In actual operation, current to the coil is switched on and off each 100 msec ., so the position of the solenoid valve is determined by the proportion of time that the signal is on as compared to the time it is off (i .e., by the duty ratio) . In other words, the valve opens wider the longer current flows to the coil . 4 . ON-OFF CONTROL VSV TYP E The construction of this type of ISC valve is as shown in the figure below . Signals from the Engine ECU cause current to flow to the coil . This excites the coil, which opens the valve, increasing the idle speed by approximately 100 rpm . (Fast-idle speed is controlled using an air valve .) Solenoid coil From air cleaner ~ To air intake chambe r OHP 7 3 104 ISC - Functions of Engine EC U FUNCTIONS OF ENGINE EC U 1 . STEPPER MOTOR TYPE ISC VALV E This type of ISC valve is connected to the Engine opening angle and vehicle speed signals that the ECU as shown in the following diagram . Target engine is idling, it switches on Tr, to Tr4, in that idling speeds for each coolant temperature and order, in accordance with the output of those air conditioner operating state are stored in the signals . This sends current to the ISC valve coil, ECU's memory. until the target idling speed is reached . When the ECU judges from the throttle valv e Engine ECU BATT Battery EFI main relayr- Microprocesso r fl B+ * IIbIIx--I Ignition switch -REL IGSW E1 Main relay control circuit \1 * Some models onl y STARTING SET-UP When the engine is stopped (no NE signal to the ECU), the ISC valve opens fully (to the 125th step) to improve sta rtability when the engine is resta rted .  Main Relay (ISC Valve Set-up) Contro l The supply of power to the ECU and ISC valve must be continued for a few moments, even after the ignition switch is turned off, in order to allow the ISC valve to be set up (fully opened) for the next engine start-up . Therefore, the ECU outputs 12 V from the M- REL terminal until the ISC valve is set up, in order to keep the main relay on . Once set-up is complete, it cuts off the flow of current to the main relay coil . OHP 74 CONDITIONS CURRENT TO MAIN RELAY Ignition switch on ON Ignition switch off O N (ISC valve set-up is I complete) OF F RELEVANT SIGNAL -*Engine speed (NE ) /- NOT E Stepper motor type ISC valves will enter a hold state when the power is interrupted . As a result, they are stopped at the position where they were when the power was interrupted . 105 ISC - Functions of Engine EC U AFTER-START CONTRO L Due to the previous set-up of the ISC valve, the amount of air passing through the ISC valve during starting is the maximum amount possible . This allows the engine to start easily . However, after the engine has started, its speed would rise too high if the ISC valve were kept fully open, so when the engine reaches a certain speed (this speed being determined by the temperature of the coolant) during or after starting, the ECU begins sending signals to the ISC valve, causing it to close from step 125 (fully open) to a point determined by the coolant temperature . For example, if the coolant temperature is 20°C (68°F) during starting, the ISC valve will gradually close from the fully-open position (step 125, or point A) to point B when engine speed reaches the predetermined level . 125 A A-B: After-sta rt contro l 20 (68 ) Coolant temperature °C (°F ) RELEVANT SIGNALS  Engine speed (NE )  Coolant temperature (THW)  Throttle position (IDL )  Vehicle speed (SPD) OHP 75 WARM-UP (FAST-IDLE) CONTRO L As the coolant warms up, the ISC valve continues to gradually close from the point to which it closed during starting . When the coolant temperature reaches about 80°C (176°F), fast- idle control by the ISC valve ends . 125 A ---------- ------------- \ A-B: After-sta rt contro l B-C: Warm-up contro l 20 80 (68) (176 ) Coolant temperature °C (°F) OHP 7 5 r-- RELEVANT SIGNALS Engine speed (NE ) Coolant temperature (THW) Throttle position (IDL) Vehicle speed (SPD ) 106 ISC - Functions of Engine ECU FEEDBACK CONTROL Feedback control is carried out when the idle contact is on, the vehicle speed is below a predetermined speed, and the coolant temperature is about 80°C (176°F) . If the difference between the actual engine speed and the target speed stored in the memory of the ECU is more than 20 rpm, the ECU sends a signal to the ISC valve, telling it to increase or decrease the volume of air passing through the bypass passage so that the actual engine speed will match the target speed . 125 A-B : After-start control B-C : Warm-up control C-D : Feedback control 11k ENGINE SPEED CHANGE ESTIMATE CONTRO L Immediately after the neutral start switch or air conditioner switch is operated, the engine load also changes . To prevent the engine speed from changing because of this, the ECU sends signals to the ISC valve to open or close it by a fixed amount before changes in the engine speed can occur . - RELEVANT SIGNALS  Engine speed (NE )  Neutral sta rt switch (NSW)  Thrott le position (IDL)  Vehicle speed (SPD)  Air conditioner (A/C ) ELECTRICAL LOAD IDLE-UP CONTRO L 20 80 (68) (176 ) A ------------------ ---------------- Coolant temperature °C (°F) OHP 7 5 Target speeds also differ depending on engine conditions, such as whether the neutral start switch is on or off, and whether the air conditioner switch is on or off. NOTE Stepper motor type ISC valves also control idle up of the air conditioner . RELEVANT SIGNALS  Engine speed (NE )  Throttle position (IDL)  Vehicle speed (SPD )  Coolant temperature (THW)  Air conditioner (A/C )  Neutral sta rt switch (NSW) Since the generating capacity of the alternator in- creases when an electrical load is applied, the Engine ECU opens the step position by a certain number of steps in order to increase the idle speed when there has been a voltage drop at the + B ter- minal or IGSW terminal or when a signal has been applied to the LP terminal, DFG terminal or ELS ter- minal . RELEVANT SIGNALS  Electrical load (LP, DFG, or ELS)  Engine speed (NE )  Throttle position (IDL)  Vehicle speed (SPD ) OTHER CONTROLS In addition to the above controls, some engines are also provided with a control in which the ISC valve operates like a dashpot during deceleration, and a control in which the ISC valve opens slightly when the oil pressure switch goes on . 107 ISC - Functions of Engine EC U 2. ROTARY SOLENOID TYPE ISC VALV E This type of ISC valve is connected to the Engine ECU as shown in the diagram below. The ISC valve carries out feedback control through duty control (from a duty ratio of 0 to 100 %) over th e Battery full idle speed range, regardless of whether the engine is cold or hot. (Air conditioner idle-up is handled by a separate idle-up device .* ) In recent models, idle up of the air conditioner is also performed by the ISC valve . OHP 7 6 STARTING CONTRO L As the engine is started, the ISC valve is opened in accordance with existing engine operating conditions, based on data stored in the ECU memory. This improves startability . - RELEVANT SIGNAL S  Coolant temperature (THW)  Engine speed (NE ) WARM-UP (FAST-IDLE) CONTRO L After the engine has started, this function controls the fast idle speed in accordance with the coolant temperature . Fu rthermore, the below-mentioned feedback control is carried out to ensure that the engine idle speed matches the target idle speed, the data for which are stored in the ECU . F RELEVANT SIGNALS Coolant temperature (THW) Engine speed (NE ) FEEDBACK CONTROL When all feedback control operating conditions have been established after the engine has started, the ECU constantly compares the actual engine speed and the target idling speed stored in its memory . The ECU sends control signals to the ISC valve as necessa ry in order to adjust the actual engine speed to match the target idling speed . In other words, when the actual engine speed is lower than the target idling speed, the ECU sends signals to the ISC valve to open it . Conversely, when the actual engine speed is higher than the target idling speed, it sends control signals to the valve to close it . Target speeds also differ depending on engine running conditions, such as whether the neutral start switch is on or off, whether the electrical load signal is on or off, and whether the air condi- tioner switch is on or off . RELEVANT SIGNALS  Engine speed (NE )  Throttle position (IDL)  Vehicle speed (SPD )  Neutral sta rt switch (NSW )  Electrical load (LP, DFG, or ELS)  Air conditioner (A/C) * * Some models onl y 108 ISC - Functions of Engine EC U ENGINE SPEED CHANGE ESTIMATE CONTROL Immediately after the neutral start switch, tail lamp relay, defogger relay or air conditioner switch is operated, the engine load also changes . To prevent the engine speed from changing becau- se of this, the ECU sends signals to the ISC valve to open or close it by a fixed amount before changes in the engine speed can occur . RELEVANT SIGNALS Neutral start switch (NSW) Electrical load (LP, DFG, or ELS )  Engine speed (NE )  Air conditioner (A/C) * * Some models onl y OTHER CONTROL S Controls other than those described above include dashpot control, which controls the ISC valve so as to prevent a sudden drop due to sudden changes in engine speed when the IDL contact in the throttle position sensor closes . In some vehicle models equipped with EHPS (electro-hydraulic power steering), the idle speed is also increased whenever the electrical load increases greatly due to the operation of the EHPS . Another control, used in some turbocharged engines, prevents the turbine from seizing up if the hydraulic pressure should drop too low to provide sufficient turbine lubrication when the idle speed returns to normal following high- speed or high-load operation . It does this by causing the idle speed to drop gradually so that the oil pump will supply a sufficient amount of oil to the turbocharger . ® ~ 1 V V 1 C 1 . When terminal T or TE1 of the check con- nector or TDCL is connected with terminal E1, the Engine ECU gradually changes the duty ratio of the ISC valve for several seconds and eventually fixed the duty ratio at a constant value . As a result, engine speed returns to the original idle speed after increasing for several seconds . 2. When the current flowing to the coil is inter- rupted due to disconnection of the ISC valve connector or other reason, the valve stops at the position at which the S or N pole of the permanent magnet is facing the core of the coil . As a result, idle speed is slightly lower when the engine is cold and slightly higher after the engine has warmed up than during normal operation . (Example: Idle speed after warm-up is approximately 1000 - 1200 rpm . ) Core Normal position Valve leve r n. W/ Guar d Permanent After magnet When cold warmed-up 109 ❑ ISC - Functions of Engine ECU 3 . DUTY-CONTROL ACV TYPE ISC VALVE The duty-control ACV controls the volume of air passing through the throttle valve by means of signals (duty signals) from the Engine ECU, and is mounted on the intake manifold . The air flow volume is determined by the ratio of the length of time that the air flow volume signal from the ECU is on to the length of time that it is off . If the idle speed has dropped due to changes in engine running conditions or changes in the electrical load (as when the air conditioner switch or neutral start switch is operated, etc .), the ACV controls the volume of air bypassing the throttle valve according to signals from th e Battery ECU, thus helping to stabilize the idle speed . (During warm-up, the fast-idle speed is controlled by the air valve .) Control is as explained below . NOTE Connecting the T (or TE1) terminal to the El terminal of the check connector or TDCL causes the ECU to fix the ACV opening angle to a certain value, regardless of engine operating conditions . OHP 7 7 STARTING CONTRO L To improve startability during cranking, STA goes on, causing the ACV to open fully . RELEVANT SIGNA L  Ignition starter switch (STA ) FEEDBACK CONTRO L The ECU changes the duty ratio of the V-ISC signal to maintain the idle speed under conditions other than starting control, engine speed change estimate control, and constant duty control . -RELEVANT SIGNAL  Engine speed (NE )  Coolant temperature (THW) ENGINE SPEED CHANGE ESTIMATE CONTROL The duty ratio changes when the air conditioner switch or neutral start switch is operated . This helps to limit changes in the idle speed . - RELEVANT SIGNAL S  Neutral sta rt switch (NSW)  Air conditioner (A/C ) CONSTANT DUTY CONTROL The ECU maintains the ACV at a fixed opening angle when the idle contact is off or the air conditioner switch is on . RELEVANT SIGNALS  Throttle position (IDL)  Air conditioner (A/C ) 110 ISC - Functions of Engine EC U 4. ON-OFF CONTROL VSV TYPE ISC VALV E The Engine ECU sends signals to the VSV, in accordance with signals from various sensors, to cause the engine to idle at the appropriate speed . Battery During warm-up, the fast-idle speed is controlled by the air valve . The following diagram shows one example of connections between the VSV and ECU . CONDITIONS FOR VSV OPERATION a . Off to On  When the engine is cranking and immediately after starting .  When engine speed falls below a predetermined rpm (depending on the neutral sta rt switch signal) with the idle contact on* .  Several seconds after shifting from "P" or "N" into any other range with the idle contact on (A/T vehicles) .*  The light control switch is turned on .  The rear window defogger switch is turne d on . * The VSV stays off under this condition if check terminals T or TE1 is connected to El . However, if the light control switch or rear win- dow defogger switch is turned on, the VSV goes on . OHP 7 8 b . On to Of f  When a predetermined period of time has elapsed after the engine has started .  When engine speed rises above a predetermined rpm (depending on the neutral start switch signal) with the idle contact on and the A/C magnetic clutch disengaged .  After a set time has elapsed after the transmission is shifted from "P" or "N" into any other range and the engine speed is above a predetermined rpm with the idle contact on and the A/C magnetic clutch disengaged (A/T vehicles) .  The light control switch is turned off.  The rear window defogger switch is turned off . 111 W NOTE ISC - Functions of Engine EC U Learned Contro l Besides the previously mentioned control, learn- ed control is also used for control of the ISC valve . Normally, the Engine ECU controls the idle speed by changing the ISC valve position . However, since the engine's running condi- tions change over time, the idle speed also changes (even though the valve positions re- main the same) . So through feedback control, the Engine ECU outputs ISC signals to return the idle speed to the target level . The ISC valve position when the target speed is reached is stored in back-up memory, and is used thereafter in idling. This is known as learned control . If all power to the Engine ECU is cut off due to the EFI fuse or STOP fuse being removed or a battery cable being disconnected, the learned value stored in back-up memory will be erased . Therefore, when the engine is restarted, the ISC valve position is set at the initial value stored in memory . At this time, the idle speed may not be the same as the target speed, but when the engine warms up and feedback control starts, it will gradually approach the target speed . 112 OTHER CONTROL SYSTEMS - Genera l OTHER CONTROL SYSTEM S GENERAL Some TCCS type engine control systems include As with the systems described up to this point, not only the EFI, ESA, and ISC systems these systems are controlled by the Engine ECU . explained so far, but also (depending on the The following table shows the specifications for engine model) the systems explained in the the 4A-FE engine . following pages . SYSTEMS PAG E (THI S MANUAL) ITEM" REMAR K ECT OD cut-off control system 11 4 Oxygen sensor heater control system 114 O Lean mixture sensor heater control system 11 4 Cut-off control 115 L ~ Air conditione r control system Magnetic clutc h relay control 11 5 EGR cut-off control system 116 With EG R Fuel octane judgment 11 6 SCV (swirl control valve) system 11 7 ACIS (acoustic control Type 1 120 induction system) Type 2 122 T-VIS (Toyota-variable induction system) 124 Turbocharging pressure control system 12 7 Supercharger control system 12 8 EHPS (electro-hydraulic power steering ) control system 12 8 AS (air suction) control system 12 9 Al (air injection) control system 12 9 * Specifications for Corolla 4A-FE engine (Apr ., 1992) 113 13 OTHER CONTROL SYSTEMS - ECT OD Cut-off Control System, Oxygen Sensor Heater Control System, Lean Mixture Sensor Heater Control Syste m ECT OD CUT-OFF CONTROL SYSTEM The Engine ECU sends an OD (overdrive) cut-off signal to the ECT ECU based on signals from the water temperature sensor and vehicle speed sensor to prohibit the transmission from shifting into overdrive. The purpose of this control is to maintain good drivability and acceleration performance . In some engines, the Engine ECU also sends a 3rd-gear cut-off signal to the ECT ECU . For fu rther details, see Step 3, vol . 4 (ECT) . ECT ECU Engine ECU OXYGEN SENSOR HEATER CONTROL SYSTE M The Engine ECU controls the operation of the oxygen sensor heater according to the intake air volume and engine speed : When the engine load is small and the exhaust gas temperature is consequently low, this heater is operated to maintain sensor efficiency . However, when the engine load and exhaust gas temperature increases greatly, heater operation is stopped to prevent deterioration of the sensor . Engine EC U Oxygen senso r Heater HT E01 and E02 J OHP 7 9 The OD cut-off signal and 3rd-gear cut-off signal appear as follows : (V) Hig h voltag e Low voltage (less than 1V ) (V) Hig h voltag e Low voltage (less than 1V) (Normal operating condition ) OD cut-off signa l L 3rd-gear cut-off signal OHP 79 LEAN MIXTURE SENSOR HEATER CONTROL SYSTE M The ECU controls the operation of the lean mixture sensor heater according to the throttle position, intake manifold pressure, engine speed, and coolant temperature signals . The temperature range in which the lean mixture sensor can operate correctly is very narrow, so the ECU keeps it within that range by controlling the amount of current that it allows to flow to the lean mixture sensor heater . 114 OHP 79 OTHER CONTROL SYSTEMS - Air Conditioner Control System 0 AIR CONDITIONER CONTROL SYSTE M 1 . CUT-OFF CONTROL 2 . MAGNETIC CLUTCH RELAY CONTRO L The Engine ECU sends a signal (ACT) to the air conditioner amplifier to disengage the air conditioner compressor magnetic clutch in order to stop operation of the air conditioning at certain engine speeds, intake manifold pressures (or intake air volumes), vehicle speeds and throttle valve opening angles . The air conditioner is turned off during quick acceleration from low engine speeds (depending on the vehicle speed, throttle valve position, and intake manifold pressure or intake air volume) . This helps maintain good acceleration performance . The air conditioner is also turned off when the engine is idling at speed below a predetermined rpm . This prevents the engine from stalling . In some engine models, magnetic clutch operation is also delayed for a predetermined length of time after the air conditioner switch is turned on. During this time, the Engine ECU opens the ISC valve to offset the drop in the engine speed due to the operation of the air conditioner compressor. This prevents the idle speed from dropping . This latter control function is called the "air conditioner compressor delay control" . +B This air conditioner control function differs from the previously-mentioned type in that the Engine ECU controls the magnetic clutch relay directly . When the Engine ECU detects the air conditioner (A/C) signal from the air conditioner control assembly, but does not detect the requisite air conditioner cut-off conditions from various sensors (see cut-off control to the left), this ECU outputs a magnetic clutch (ACMG) signal to the magnetic clutch relay, turning it on . As a result, the magnetic clutch goes on and the air conditioner compressor operates . This air conditioner control function is also provided with an air compressor delay control . The operation of this is the same as that in th e air conditioner cut-off control function . +B OHP 8 0 OHP 80 115 © OTHER CONTROL SYSTEMS - EGR Cut-off Control System, Fuel Octane Judgmen t EGR CUT-OFF CONTROL SYSTEM This system actuates the VSV, which therefore causes atmospheric air instead of intake manifold vacuum to act on the EGR (exhaust gas recirculation) vacuum modulator . This shuts off the EGR to maintain drivability when the engine coolant is cold or during high-speed driving etc . OPERATION The Engine ECU actuates the VSV, shutting off the EGR when the coolant temperature is below a predetermined temperature or when the engine speed is above a set speed (roughly 4,000 to 4,500 rpm), to maintain drivability . The ECU also actuates the VSV to shut off the EGR when the intake air volume is above a predetermined level or when the fuel cut-off function is on in order to maintain EGR valve durability . Thro tt le valv e l EGR vsv ~- .n, .+~ ~ i ~. .,~ EGR valve Air intake chamber i Sensors Exhaust gas EGR ' ECU S Battery OHP 8 1 REFERENCE Some recent models use stepper motor type EGR valves . An EGR vacuum modulator and VSV are not provided in this system . The Engine ECU controls EGR volume and cut-off . In addition, when current is not applied to the EGR valve, the valve is fully closed by the force of a return spring . Exhaust ga s FUEL OCTANE JUDGMEN T The Engine ECU in some engine models determines the octane rating of the gasoline being used (whether it is "premium" or "regular") according to engine knocking signals from the knock sensor . OPERATIO N The ECU judges whether the gasoline is "premium" or " regular" based on the retard angle of the ignition timing, which is determined by the strength of engine knocking when the coolant temperature is above a predetermined temperature . It judges the gasoline to be "regular" when the engine knocks severely an d the retard angle is larger than a predetermined value. It judges the gasoline to be "premium" when the engine knocks only mildly and the retard angle is smaller than a predetermined value . The ECU stores the result of this judgment until it judges that the octane rating of the gasoline has changed . 116 OTHER CONTROL SYSTEMS - SCV System SCV (SWIRL CONTROL VALVE) SYSTE M The intake port has been divided longitudinally into two passages as shown in the following illustration . The swirl control valve, which is opened and closed by the intake manifold vacuum, is mounted in passage ;A . Exhaust valve Swirl control ~ Intake valv e valve (closed) ® When the engine is running under a light load or below a certain rpm, this valve closes, creating a powerful swirl . This increases combustion efficiency, thereby improving fuel economy . Under a heavy load or over a certain rpm, the valve opens, increasing intake efficiency, and thus improving engine output . A swirl control valve is provided in the intake port of each cylinder . Swirl control lin k Intake port Passage B Passage B OHP 82 OHP 8 2 Throttle position sensor Manifol d pressure sensor valve Swirl control valve OHP 82 117 rr ACIS (ACOUSTIC CONTROL INDUCTION SYSTEM ) The ACIS changes the effective length of the here for convenience "Type 1" and "Type 2" . intake manifold in order to increase air intake They differ both in their basic design and in the efficiency. There are two types of ACIS, called number of air control valves used . 1 . TYPE 1 GENERAL This type of ACIS has only one air control valve. distributor. This air control valve is opened and This is located in the air intake chamber and is closed by the Engine ECU via a VSV and an used to increase the intake efficiency of the air actuator . supplied to the cylinders . It does this in response This makes it possible to improve engine to changes in the throttle opening (VTA) signal performance at both low and high engine sent from the throttle position sensor, and the speeds . engine speed (NE) signal sent from the Thro ttle valve Air control valv e Distributo r e1Z 11 F VTA N E Engine ECU 4 Actuator OHP 8 4 Vacuum tan k Vs V ~ a~ b tf664@ Air control valve Air control valv e closed OTHER CONTROL SYSTEMS - ACI S Air contro l \valve Actuator VsV Vacuum tank OHP 84 Throttle position senso r Low Engine speed ~ High OHP 8 4 120 OTHER CONTROL SYSTEMS - ACI S OPERATIO N The ECU turns the VSV on or off, depending on the throttle opening angle and the engine speed, as explained below : Set spee d VSV: o n (Air control valve: closed ) VSV: off (Air control valve: open ) Low- VSV: off (Air contro l valve : open ) VSV: o n (Air contro l valve: closed ) Engine speed - High OHP 8 5 1! VSV turned on Closing air control valve has the same effect as lengthening the intake manifold . OHP 85 2, VSV turned off Opening air control valve has the same effect as shortening the intake manifold . (open ) Air control valv e OHP 85 121 2 . TYPE 2 GENERAL OTHER CONTROL SYSTEMS - ACI S In this type of ACIS, the air control valves are located in front of the No. 2 air intake chamber . By opening and closing these valves i n No. 2 air intake chamber OHP 86 (Po OHP 8 7 Cross section A-A' No. 1 air intake chamber Air control valves Vacuum tan k P Fro m air [--> cleaner Intak e manifold accordance with engine running conditions, the same effect as lengthening or shortening the intake manifold (as in Type 1) can be obtained . Air control valve s Combustion chamber Vs V Actuator Engine ECU Engine spee d OHP 86 122 OTHER CONTROL SYSTEMS - ACI S OPERATION 1 Low and medium speeds (below set speed) The ECU turns the VSV on when the engine is running at low to medium speeds . Therefore, the vacuum (supplied by the vacuum tank) causes the actuator to close the air control valves fully . By closing the air control valves, the same effect as lengthening the intake manifold is obtained . This improves intake efficiency in the low- and medium-speed ranges . Thrott le valve Air contro l No. 1 air intake valve (closed) chamber 1-Z No . 2 air a~ intak e chamber OHP 87 2 High speed (above set speed ) When the engine speed rises above the predetermined speed, the ECU turns the VSV off and the atmospheric air acts directly upon the actuator. Therefore, the spring damper causes the actuator to open the air control valves fully . By opening the air control valves, the same effect as shortening the intake manifold is obtained. This shifts the peak intake efficiency to the high engine speed range, improving output in the high-speed range . OHP 87 1 23 OTHER CONTROL SYSTEMS - T-VI S T-VIS (TOYOTA-VARIABLE INDUCTION SYSTEM ) GENERAL a . The intake manifold passage leading to each cylinder is divided into two parts. One of these (the variable induction passage) is provided with an intake air control valve . This valve opens and closes in accordance with the speed of the engine, thus acting as a variable induction valve. This makes it possible to improve engine performance in the low-speed range without sacrificing the high engine speed and output that are distinctive features of engines with four valves per cylinder . VSV Intake manifol d (air intake chamber) T-VIS b. The intake air control valves for all cylinders are constructed as one unit, and are opened and closed together by an actuator . c . The improvement in the pe rformance of the engine due to the adoption of T-VIS is shown in the graph below . OHP 88 Low Engine speed --- High OHP 8 8 OHP 8 8 Engine EC U 124 OTHER CONTROL SYSTEMS - Turbocharging Pressure Control Syste m TURBOCHARGING PRESSURE CONTROL SYSTEM The Engine ECU turns the VSV on and off* to This maximizes engine performance and control the turbocharging pressure in accordance maintains engine durability, as well as with the type of gasoline being used (regular or suppressing knocking under all engine running premium), the coolant temperature, intake air conditions, including warm-up, irrespective of temperature, intake air volume, and engine the gasoline octane rating . speed . The VSV is controlled with the duty ratio in some models . Turbocharge r OPERATION The VSV is turned on by the ECU to increase the The VSV does not turn on unless all of the abov e turbocharging pressure when the fuel is judged to be premium by the fuel octane judgment function (See page 116), and when the coolant temperature and intake air temperature are within a predetermined temperature, and the intake air volume is above a predetermined level . conditions are met, even when premium gasoline is used . REFERENCE For a detailed explanation of the construction and operation of the turbocharger, see Step 3, l .. 2 (Turbocharger and Supercharger) . vo 127 OTHER CONTROL SYSTEMS - Supercharger Control System, EHPS Control Syste m SUPERCHARGER CONTROL SYSTEM The Engine ECU controls the supercharger relay, thus turning the supercharger magnetic clutch on and off. It also controls supercharger operation by controlling the supercharger bypass valve (stepper motor type) . In addition, the ECU controls the ACV to reduce supercharger oil consumption . Suspercharger bypas s valve (stepper motor type) Engine EC U AB,, A8 z +B AC V (Air control valvel Intercooler AB3, AB 4 Supercharge r magnetic clutc h rela y Supercharge r +B Supercharger magnetic clutch ACV D 0 REFERRENCE In previous models, VSV and ABV (air bypass valve) have been used instead of a super- charger bypass valve . For a deteiled explanation of the construction and operation of the supercharger, see Step 3, vol . 2 (Turbocharger and Supercharger) . SMC Drive pully EHPS (ELECTRO-HYDRAULIC POWER STEERING) CONTROL SYSTEM In vehicles equipped with the EHPS, when the engine coolant temperature or the engine speed is very low, the load on the alternator is increased when the vane pump motor of the EHPS is driven . This condition makes it easier for poor engine startability or engine stalling to occur. To prevent this, the vane pump motor is stopped during cold starting or when the engine speed is extremely low . PS ECU Engine EC U OHP 90 REFERENCE EHPS is a type of power steering in which the vane pump is driven by an electric motor . 128 OTHER CONTROL SYSTEMS - AS Control System, Al Control Syste m AS (AIR SUCTION) CONTROL SYSTE M The AS system is operated by the ECU when exhaust emissions tend to increase ; e.g., when the engine is cold and during deceleration . Under other operating conditions, this system does not operate to prevent overheating of the TWC (three-way catalyst) . 4 Al (AIR INJECTION) CONTROL SYSTE M The Al system is operated by the ECU when exhaust emissions tend to increase ; e .g ., when the engine is cold and during deceleration . Under other conditions, this system does not operate to prevent overheating of the TWC . OPERATION * OPERATION * The ECU switches on the VSV for the AS system and operates the AS system when all of the following conditions are met : a . Engine col d  Coolant temperature below 35°C (95°F)  ER power enrichment not operating .  Engine speed below a predetermined level . b . Deceleratio n  Coolant temperature above 35°C (95°F )  IDL contact closed (accelerator pedal com- pletely released . )  Engine speed between about 1000 and 3000 rpm . * Depending on the engine models . VSV Reed valv e r VSV OHP 9 1 From air cleaner AS valve When it is activated by the ECU, the VSV introduces intake manifold vacuum into the ASV (air switching valve) diaphragm chamber . This causes the air discharged by the air pump to pass through the check valve and be injected into the cylinder head's exhaust port. If the supply of current to the VSV is stopped, atmospheric air is introduced into the ASV's diaphragm chamber and the passage to the air injection exhaust port is closed off, resulting in the discharged air pushing against the spring inside the ASV and being discharged outside through the silencer . * Depending on the engine models . From air cleaner 129 11 OTHER CONTROL SYSTEMS - Al Control Syste m REFERENCE There are some recent models in which the Engine ECU sends the vehicle speed signal or engine speed signal to combination meter . The combination meter then operates the speedometer and tachometer based on these signals . 130 DIAGNOSIS - Genera l DIAGNOSIS GENERAL The ECU contains a built-in diagnostic system . Depending on the vehicle model, the diagnostic system has a normal mode only, or it can have a normal mode and a test mode . In the normal mode, the ECU (which is constantly monitoring most sensors) lights the "CHECK ENGINE" lamp when it detects a malfunction in certain sensors or their circuitry . At the same time, the ECU registers the system containing the malfunction in its memory . This information is retained in memory even after the ignition switch is turned off . When the vehicle is brought into the shop because of trouble in the engine control system, the contents of the memory may be checked to identify the malfunction . "CHECK ENGINE" lamp OHP 9 2 The "CHECK ENGINE" lamp does not light when certain malfunctions are detected (See pages 138 to 140), because those malfunctions would not cause any major trouble such as engine stalling . After a malfunction is corrected, the "CHECK ENGINE" lamp turns off. However, the ECU memory retains a record of the system in which the malfunction occurred . ® In most engines, the contents of the diagnostic memory can be checked by connecting terminal T or TE1 with El of the check connector or TDCL (Toyota diagnostic communication link) and counting the number of times the "CHECK ENGINE" lamp blinks . OHP 9 2 ,- -rvv 1 r In the case of OBD-II used for vehicles sold in the U .S .A. and Canada, an OBD-II scan tool or TOYOTA hand-held tester is required to read diagnostic codes (See page 137-2) . In some older model engines, the contents of the diagnostic memory can be checked by connecting a service wire to terminals T and El of the check connector and an analog voltmeter to terminals VF and El of the EFI service connector, then checking the voltage fluctuations . In recent models, a test mode function has been added to the functions of the diagnostic system for the purpose of detecting intermittent problems (such as poor contact) which are difficult to detect in the normal mode . CHECK 7 ENGIN E ~ 131 0 DIAGNOSIS - General, Principle of Diagnostic Syste m The test mode is used only by the technician for troubleshooting the engine control system . Compared to the normal mode, it has been given a greater sensitivity . For example, in the normal mode, the ECU will light the "CHECK ENGINE" lamp and register the problem in memory if the same trouble is detected two times in succession ; in the test mode, however, the ECU will light the "CHECK ENGINE" lamp and register it in memory if the trouble is detected even once . The test mode is made operative by the technician by means of a predetermined procedure . The method of reading the diagnostic codes in the test mode is the same as in the normal mode. The methods for utilizing the normal mode and test mode is explained in the TROUBLESHOOTING section (page 149) . The items which cause the ECU to light the "CHECK ENGINE" lamp and the items registered in memory when the ECU detects trouble differ depending on the mode as well as on the vehicle model . Please refer to the repair manual for the affected vehicle . See CHECKING AND CLEARING DIAGNOSTIC CODES (page 159) for the normal mode and test mode setting procedure, code output methods, and code clearing methods . In addition, various types of information are output by the VF terminal of the check connector, depending on the state of the T or TE1 terminal and the state of the IDL contacts of the throttle position sensor. For details, see VF OR VF1 TERMINAL OUTPUT in this section (page 136) . PRINCIPLE OF DIAGNOSTIC SYSTEM The signal level that signifies to the ECU that an input or output signal is normal is fixed for that signal . When signals for a particular circuit are abnormal with respect to this fixed level, that circuit is diagnosed as being abnormal . For example, when the coolant temperature signal circuit is normal, the voltage at the THW terminal is in a fixed range between 0 .1 to 4 .9 V . This signal circuit is diagnosed as being abnormal when the THW terminal voltage is less than 0.1 V (a coolant temperature of 139°C [282°F] or greater) or greater than 4 .9 V (a coolant temperature of -50°C [-58°F] or lower) . 5 ~+r Abnormal rang e 4 THW Normal range / for engin e Normal range /( Normal rang e for diagnostic system for diagnostic syste m 3 2 1 0' -~ ~ Abnormal range i -50 139 (-58) (282 ) Coolant temperature °C (°F ) -50°C~ / r ~ ~(-58°F~/ Normal range 139°C (282°F Abnormal 4.9 V OHP 92 132 DIAGNOSIS - "CHECK ENGINE" Lamp and VF or VF1 Terminal Output "CHECK ENGINE" LAMP AND VF OR VF1 TERMINAL OUTPU T The "CHECK ENGINE" ► amp and the output voltage of the VF or VF1 terminal have the following functions which differ depending on the state of the T, TE1 or TE2*5 terminal (of-the check connector or TDCL) and the idle contact in the throttle position sensor . TorTE1 TE2+5 IDL "CHECK ENGINE" LAMP VF or VF1 TERMINAL OUTPU T TERMINAL TERMINAL CONTACT 5 V Increased injectio n volum e 3 .75 V Increased injectio n Off volum e Norma l  Bulb check function 5 V 2 ---------------------- -------- - (en ne stopped ) 9i Results of air-fuel . Air-fuel ratio feedbac k Off  Warning display function ratio learned control 1 correction stopped * z (open) with normal mode sed injectio n Off (engine operating) 1 .25 V Dolum e (open) Decreased injectio n On volum e 0 V --- ------ - - --- -- - ------- - Air-fuel ratio feedbac k correction stopped + 2 On Off  Bulb check function (TE2 and El ( engine stopped ) di l f i i  W i ECU d E sp unct o n arn ng ay ng ne at a terminals O test mode wit h connected) n ( engine operating) Results of oxygen sen- 5 V Rich signa l i l i sor s gna process ng 0 V Lean signal or openloo p operation * 4 Diagnostic code display function ---------------------------- ------- --- ---------------------------------- - Off with normal mode *' 5V Feedback correction no t Off Results of lean mix- o r 5 V 2 taking plac e On ture sensor signal pro- . (open ) IT or TE1 cessing 0 V Feedback correctio n and E1 taking plac e terminal s connected) 5 V Norma l l f di i On Resu ts o agnost c 0 V Malfunction code store d On Off (TE2 and E1 Diagnostic code display function ECU d E i at a ng n e terminals connected) On with test mod e *t Some systems have five levels, as shown here, while other systems have only three levels (0 V, 2 .5 V and 5 V) . `2 The VF or VF1 terminal output when air-fuel ratio feedback correction is not being carried out is either 0 V or 2 .5 V, depending on the vehicle . *3 Some models do not display diagnostic codes when the idle contact are off . *4 "Open-loop operation" refers to the state in which the oxygen sensor signal is not being used for control (See page 75) . 50n1y models having a test mode . 133 DIAGNOSIS - "CHECK ENGINE" Lamp and VF or VF1 Terminal Outpu t 1 . "CHECK ENGINE" LAMP FUNCTION S LAMP CHECK FUNCTION (T or TE1 terminal off ) The "CHECK ENGINE" lamp goes on when the ignition switch is turned on to inform the driver that it has not burnt out . It goes out again when the engine speed reaches 500 rpm . (The engine speed may differ in some engine models . ) Bulb burnout ~* c 500 rpm 1 - About L cK About 200 rpm OHP 9 3 WARNING DISPLAY FUNCTION IT or TE1 terminal off) When trouble occurs and the ECU has detected its occurrence in one of the input/output signal cir- cuits connected to the ECU (that is, one of those marked "ON" in the "CHECK ENGINE" LAMP col- umn of the table on page 138), the "CHECK ENGINE" lamp goes on to aleart the driver . The lamp goes off when conditions are restored to nor- mal. (This occurs only at an engine speed of 500 rpm or higher) . DIAGNOSTIC CODE DISPLAY FUNCTION (T or TE1 terminal on ) If the T or TE1 terminal is connected to the El terminal (after the ignition switch is turned on), diagnostic codes are displayed in order from the smallest to the largest code, with the number of times the "CHECK ENGINE" lamp blinks indicating the malfunction code number. In some engines, a test mode has been provided which makes the diagnostic system more sensitive. This system is also provided with a TE2 terminal in the TDCL or check connector . See CHECKING AND CLEARING DIAGNOSTIC CODES (page 159) for the normal mode and test mode setting procedure and the code output methods . REFERENCE Super Monitor Displa y When the results of a diagnostic output from the warning lamp terminal (terminal W) are displayed on a super monitor, the diagnostic code display will not appear on the monitor, if the injection signal is input to the Super Monitor ECU by the Engine ECU even once . + B Super Monito r Engine ECU ~z ECU Switches J 2-TRIP DETECTION LOGI C Some diagnostic codes, such as codes 21 and 25 (See page 138), use "2-trip detection logic" . With this logic, when a malfunction is first detected, it is temporarily stored in ECU memory . If the same malfuntion is detected again, this se- cond detection causes the "CHECK ENGINE" lamp to light up. (However, the ignition switch must be turned off between the 1 st time and 2nd time) . 1st malfunction detection (temporaril y recorded ) IG SW on 2nd malfunction detection (warning light lights up ) Drivin g pattern IG SW IG SW IG SW off on of f OHP 9 3 In the test mode, the "CHECK ENGINE" lamp lights up the 1st time a malfunction is detected . 134 DIAGNOSIS - "CHECK ENGINE" Lamp and VF or VF1 Terminal Outpu t DIAGNOSTIC MODE AND "CHECK ENGINE" LAM P The diagnostic mode (normal or test) and the See CHECKING AND CLEARING DIAGNOSTIC output of the "CHECK ENGINE" lamp can be CODES (page 159) for the normal mode and test selected by changing the connections of the T or mode setting procedure and the code output TE1, TE2 and El terminals on the check methods . connector or TDCL, as shown in the table below . T OR TE1 AND El TE2 AND El DIAGNOSTIC "CHECK ENGINE" LAM P TERMINALS TERMINALS MOD E Open Normal Warns driver of malfunctio n Open Connected Test Notifies technician of malfunctio n Open Normal Outputs diagnostic results (nature of malfunction), b y number of times lamp blinks . Connected Connected Test Outputs diagnostic results (nature of malfunction), by number of times lamp blinks . 135 DIAGNOSIS - "CHECK ENGINE" Lamp and VF or VF1 Terminal Outpu t 2 . VF OR VF1 TERMINAL OUTPUT OUTPUT OF AIR-FUEL RATIO FEEDBACK CORRECTION (T, TE1 or TE2 terminal off ) The air-fuel ratio feedback correction amount is output in three or five levels from the VF or VF1 terminal of the check connector. When the value is normal, the output is constant at 2 .5 V, but when the output is greater than 2.5 V, it indicates that feedback correction is on increase side, while an output lower than 2 .5 V indicates that feedback correction is on decrease side . Increasing 5 .0 V 3.75 V 2 .5 V 1 .25 V Decreasing 0V OHP 9 3 On engines which include a vane type air flow meter, when the VF voltage is other than 2 .5 V, this voltage can be adjusted by tightening the idle mixture adjusting screw on the air flow m ete r . The VF or VF1 terminal output when air-fuel ratio feedback correction is not being performed is either 0 V or 2.5 V, depending on the vehicle model . Some vehicle models also have a VF2 terminal . In V-type engines with a VF2 terminal, the VF1 terminal outputs information on the left bank cylinders and the VF2 terminal outputs information on the right bank cylinders . In in-line 6-cylinder engines with a VF2 terminal, the VF1 terminal outputs information on the No . 1 to No. 3 cylinders, and the VF2 terminal outputs information on the No . 4 to No. 6 cylinders . T E 1 . When adjusting the idle mixture adjusting screw, turn it slowly, a little at a time . If this screw is turned too quickly, air-fuel ratio feedback correction will be halted and you will not be able to adjust the VF voltage . 2. In vehicles in which the idle mixture adjusting screw is sealed, the ECU automatically adjusts the idle mixture . Therefore, it is not necessary to adjust the idle mixture . -REFERENCE VF or VF1 Terminal Voltag e When measured on an oscilloscope, the output waveform of the VF or VF1 terminal voltage has a constant period of approximately 32 msec (depending on the engine model), as shown in the figure below . 4 V 2 V 0V 20 msec . I I I __1 +---i 32 msec . When a voltmeter is used to measure the value, a virtually constant value is displayed . 136 DIAGNOSIS - "CHECK ENGINE" Lamp and VF or VF1 Terminal Outpu t OXYGEN SENSOR SIGNAL OUTPUT IT or TE1 terminal on, TE2 terminal off, idle contact off ) To read the output of the oxygen sensor, connect terminal T or TE1 with terminal El, with the idle contact off. Then measure the voltage at the VF or VF1 terminal . (The output from this terminal is not the actual signal that is output by the oxygen sensor, but a signal that has been digitalized by the ECU for easier reading . ) This signal is 5 V when the input signal from the oxygen sensor is higher than the comparison voltage set by the ECU, and is 0 V when the input signal is lower than the comparison voltage or during an open-loop operation . Comparison voltag e 0V (lean ) VF or VF1 terminal voltage OHP 93 When using a voltmeter to check air-fuel ratio feedback correction, first warm up the oxygen sensor by warming up the engine, then, while maintaining engine speed at 2,500 rpm to keep the idle contact off, measure the VF voltage . (See page 182 for the method of outputting this signal . ) LEAN MIXTURE SENSOR SIGNAL OUTPUT (T or TE1 terminal on, TE2 terminal off, idle contact off ) This signal is 0 V while air-fuel ratio feedback correction is taking place, and 2 .5 V or 5 V when air-fuel ratio feedback correction is not taking place . (See page 183 for the method of outputting this signal .) DIAGNOSIS OUTPUT (T or TE1 terminal on, TE2 terminal off, idle contact on ) J Output of result s Connecting the T or TE1 terminal to the El terminal causes the ECU (VF or VF1 terminal) to signal whether there are any data in the diagnostic memory or not. If all the diagnostic results are normal, a 5 V signal will be output, but if any malfunction codes are stored in memory, a 0 V signal will be output (that is, the voltage at the VF or VF1 terminal will fall to zero) . ~2 Diagnostic code number outpu t In older model engines, diagnostic results are read by connecting an analog voltmeter to the VF terminal and counting the number of oscillations of the needle of the voltmeter . This number corresponds to the trouble code number, which can then be looked up to identify the trouble . See the relevant repair manual concerning the output method for the diagnostic codes and display format . 137 141 DIAGNOSIS - "CHECK ENGINE" Lamp and VF or VF1 Terminal Outpu t ENGINE ECU DATA OUTPUT (TE2 terminal on ) In engines having a test mode for diagnosis, the Engine ECU has the function to output data calculated according to signals from each sensor . Output data accounts for a portion of input data from sensors and output data to actuators . Since the data is output in the form of serial communica- tions, it cannot be read without using a TOYOTA hand-held tester, DIAGNOSIS READER or DIAGNOSIS MONITOR . Refer to the Repair Manual or the Handling Manual of a TOYOTA hand-held tester, DIAGNOSIS READER or DIAGNOSIS MONITOR for information on the reading procedure and out- put parameters . ~ REFERENCE I Serial Communication : Serial communication is one of digital com- munication . One piece of data is sent by com- bining high (1) and low (0) signals for each unit time (t) . Multiple pieces of data can be sent with a single communication line . Hig h Low J t' t2 t3 / DIAGNOSIS - OBD-I[ (On-Board Diagnostic System ) FO REFERENCE BD- If (On-Board Diagnostic system ) OBD regulations refer to those regulations used in the U .S .A . In order to detect if the vehicle is emitting harmful exhaust gases into the atmosphere, the OBD system enables the Engine ECU *' to detect any malfunctions of the engine and exhaust control systems and warn the driver of such conditions via the "CHECK ENGINE" lamp * z . There are two types of OBD regulations, namely OBD- I and OBD-I[ . OBD- I regulations are satisfied with the diagnostic system that has been conventionally used by Toyota. OBD-II regulations require the functions shown in the table below against OBD- I regulations . * i *z SAE term ; ECM (engine control module) SAE term ; MIL (malfunction indicator lamp) 0= Required . x = Not require d Required item OBD- I OBD-II  Detect malfunctions and turn on "CHECK ENGINE" lamp 0 ( 8 items) 0 (41 items )  Standardize malfunction codes x 0  Output Engine ECU data x 0 (17 items )  Freeze-frame data* x 0 (13 items )  Communicate between Engine ECU and diagnostic tool x 0  Standardize diagnostic tools x 0  Standardize diagnostic connectors x 0 *An Engine ECU function to store important control data into internal memory during the detection of a malfunction . The main characteristic of OBD-II is the unifica- tion of diagnostic codes and the use of a special-purpose tester . As a result, communica- tion protocol between the tester and the DLC (Date Link Connector) and Engine ECU are stan- dardized . Furthermore, in the case of OBD-II, measurement of engine rpm and inspection of each function of the Engine ECU cannot be per- formed without using a special-purpose tester . Toyota employs a system in which original functions have been added to those required by OBD-II regulations. The following describes some of the major differences between Toyota's conventional OBD system and the new OBD system (OBD-II) provided in vehicles sold in the U .S.A. and Canada . 4 DIAGNOSIS - OBD-II (On-Board Diagnostic System ) Conventional OBD New OBD (OBD-II ) CHECK ENGINE When a proble m LAMP has been detected Lights Lights or blink s When the proble m has been solved Goes off after about 5 seconds Goes off after 2 or 3 trip s DIAGNOSTIC Code 2 digits ( e .g . : 25, 31) 5 digits (e .g .: P0120 ) CODE Reading operation Connection of terminal TE 1 and terminal E l Code display "CHECK ENGINE" lamp blink s Code clearing*' Removal of memory fuse OBD-II scan tool o r TOYOTA hand-held teste r ENGINE ECU Reading operation Connection of terminal TE 2 DATA and terminal E l Reading DIAGNOSIS REDER, DIAGNOSI S instruments MONITOR, or TOYOTA hand-hel d tester Output terminal Terminal VF Terminal SDL* 2 Communication Slow (about 1 .5 seconds) Fast ( about 0.05 to 1 .0 seconds ) rate Data display Few Man y item s Data display method Toyota standard SAE standar d ACTIVE TEST*3 Not available Available (performed using a n OBD-II scan tool or TOYOT A FREEZE-FRAM DATA Not available hand-held tester ) * i + z 3 In the case of a new OBD (OBD-II), diagnostic codes can also be cleared by removing the memory fuse in the same manner as the conventional OBD . SDL ; The communication terminal between the Engine ECU and the TOYOTA hand-held tester use the VPW ( Variable Pulse Width) system in accordance with the SAE J1850 requirements . Actuators (injector, ISC valve, etc .) are operated by sending a signal from the tester to the Engine ECU . DIAGNOSIS - OBD-I[ (On-Board Diagnostic System ) Conventional OBD New OBD (OBD-I[ ) CHECK CHECK W E1 OX1 CC2 IG- TE1 E l CONNECTOR CONNECTOR TEl O (DLC) AND (DLC 1 ) TER MINAL tM FP D (Only those CC related to the +B lJ CD Engine ECU) VF1 VF2TE2OX2 TT + B TDCL ECT W (DLC2) ENG TT E1 TE2 TE1 E l DLC3 BATT SDL* ' ?CG* 3 SDL ; The communication terminal between the Engine ECU and the TOYOTA hand-held tester use the VPW (Variable Pulse Width) system in accordance with the SAE J1850 requirements . *zSG ; Signal graund *3CG ; Chassis graund DIAGNOSIS - Diagnostic Code s DIAGNOSTIC CODE S The "CHECK ENGINE" lamp lights up when trou- ble occurs. It goes off again 5 seconds after the relevant system is restored to normal . (Remember, however, that when the engine speed is lower than 500 rpm, the lamp may light up for the bulb burnout check . ) If two or more problems have occurred and are stored in memory, the malfunction codes will be displayed in order from the smallest code . Code numbers and their meanings for the 4A- FE engine (Corolla AE101 for Europe) are as shown in the following table . Diagnostic items and the meanings of the malfunction codes differ depending on the engine model . For details, see the Repair Manual for the relevant engine . (As Feb ., 1992 ) C E NGINE " "C H CODE NUMBER OF TIME S "CHECK ENGINE" LAMP CIRCUITRY LA~ P DIAGNOSIS 2 NO . BLINKS NORMAL TEST (MEANING OF TROUBLE CODE) TROUBLE AREA MEMOR Y MODE MODE - J Ll LI LI LI LJ LI LI L Normal - - Output when no other code is recorded . - -  No "NE" signal to ECU within 2 seconds  Open or short in NE, G after engine is cranked . circuit 12 RPM signal ON N .A .  No "G" signal to ECU for 3 seconds when  IIA 0 the engine speed is between 600 rpm and  Open or short in STA 4000 rpm . circuit  ECU ON N .A . No "NE" signal to ECU when the engin e speed is above 1 500 rpm .  Open or short in NE circui t 13 n n n n RPM signal No "G" signal to ECU while "NE" signal is  IIA 0 N .A . ON input 4 times to ECU when engine speed is  EC U between 500 rpm and 4000 rpm .  Open or short in IGF or IG T 14 n UJ j L_ Ignition signal ON N .A . No " IGF" signal to ECU 4 times in succession . circuit from igniter to ECU O  Ignite r  ECU  Open or sho rt in heate r N .A . Open or short circuit in oxygen sensor heater circuit of oxygen senso r wire (HT) .  Oxygen sensor heater rI Oxygen  ECU 21 n n sensor OFF During air-fuel ratio feedback correction, O circuit output voltage of oxygen sensor remains  Open or short in oxyge n ON between 0 .35 V and 0 .7 V continuously for a sensor circuit ce rt ain period .  Oxygen senso r " (2 trip detection logic)  EC U  Open or short in wate r 22 n n n n Water temp . ON ON Open or sho rt circuit in water temp . sensor temp . sensor circuit sensor signal signallTHWI .  Water temp . sensor 0  ECU Intake air  Open or short in intake ai r 24 temp . sensor OFF ON Open or sho rt circuit in intake air temp . sensor temp . circuit 0 signal signal ( THA) .  Intake air temp . senso r  ECU  Engine ground bolt loos e  Open in E1 circui t Oxygen sensor output is less than 0.45 V for  Open in injector circuit 25 J U LJ I.J IJ U LJ L Air-fue l ratio lean OFF ON at least 90 secs . or more when oxygen sensor  Fuel line pressure (Injector blockage, etc .) 0 malfunction is warmed up (racing at 2,000 rpm) . 3 *3 (2 trip detection logic)  Open or short in oxygen sensor circuit  Oxygen senso r  Ignition syste m Vacuum  Open or short in vacuu m 31 n n n n sensor ON ON Open or short circuit in manifold pressure sen- sensor circuit O signal sor signal ( PIM) .  Vacuum senso r  EC U 138 DIAGNOSIS - Diagnostic Code s "CHECK ENGINE" , z CODE NUMBER OF TIME S _ " UITRY LAMP" DIAGNOSIS TROUBLE AREA MEMORY NO . CHECK ENGINE LAMP CIRC NORMAL TEST (MEANING OF TROUBLE CODE ) BLINKS MODE MODE Throttle  Open or short in throttl e nn r Jn n ULI LI LJ L position OFF ON Open or short circuit in throttle position position sensor circuit 0 41 -- sensor sensor signal (VTA ) .  Throttle position senso r signal  EC U OFF N A No "SPD" signal to ECU for 8 seconds whe n . . vehicle is running .  Open or short in vehicle rI rI fl rl r1 f1 Vehicle speed speed sensor circuit Q,  42 J ll lJ ll LJ U L- sensor signal  Vehicle speed senso r N A OFF No "SPD" signal input to ECU after ignition  EC U . . switch is turned on .  Open or short in starte r 43 nn~7n nn n J LI LI u L~ u U L Starter signal N .A . OFF No "STA" signal input to ECU after ignition signal circui t  Open or short in IG SW or x switch is turned on . main relay circui t  ECU  Open or sho rt in knoc k With engine speed between 1,200 rpm and sensor circui t 52~ Knock sensor ON N .A . 6,000 rpm, signal from knock sensor is not  Knock sensor (looseness, 0 signal input to ECU for cert ain period . ( KNK) etc . )  ECU Displayed when A/C is ON, IDL contact OFF or ~ A/C switch syste m Switch "R", "D", "2", or "L" rang e shift lever is in Throttle position senso r 51's~_ condition N .A . OFF and STA is OFF with the check terminals El IDL circuit x signals and TE1 connected at test mode .  Accelerator pedal, cabl e  ECU + 1 * 2 * 3 *4 5 "ON" displayed in the diagnosis mode column indicates that the "CHECK ENGINE" lamp is lighted up when a malfunction is detected . "OFF" indicates that the "CHECK ENGINE" lamp does not light up dur- ing malfunction diagnosis, even if a malfunction is detected . "N .A ." indicates that the item is not includ- ed in malfunction diagnosis . Lighting of the "CHECK ENGINE" lamp varies depending on engine models and the destinations . " 0" in the memory column indicates that a diagnostic code is recorded in the ECU memory when a malfunction is detected . " x" indicates that a diagnostic code is not recorded in the ECU memory even if a malfunction is detected . Accordingly, output of diagnostic results in normal or test mode is perform- ed with the ignition switch ON . "2 trip detection logic" (See page 134) is only active at the normal mode . Not stored in memory at the test mode . IDL contact off is not detected until after the engine starts . 139 DIAGNOSIS - Diagnostic Codes ncrcnicrv%,c Examples of diagnostic codes of OBD-II com- OBD-II system has a check mode function in patible engines in vehicles sold in the U .S.A . which detection of a problem has greater sen- and Canada are show below . In the same sitivity than the normal mode . manner as the conventional OBD system, th e  Camry 1 MZ-FE engine (1994 model year ) COD E NO CIRCUITRY "CHECK ENGINE" DIAGNOSIS TROUBLE AREA MEMOR Y . LAMP  ~ (MEANING OF TROBLE CODE ) P0100 Mass air flow circuit ON Open or short in mass air flow meter circuit with  Open or short in mass air flow meter circui t malfunction engine speed 4,000 rpm or less  Mass air flow meter 0  ECU Conditions a) and b) continue with engine spee d Mass air flow circuit 900 rpm or less : P0101 range/performance ON (2 trip detection logic) `3  Mass air flow meter 0 problem a) Closed throttle position switch : O N b) Mass air flow meter output > 2 .2 V  Open or short in intake air temp . senso r P0110 Intake air temp . circuit lf i ON Open or short in intake air temp . sensor circuit circuit O ma unct on  Intake air temp . senso r  ECU  Open or short in engine coolant temp . P0115 Engine coolant temp . ON Open or short in engine coolant temp . sensor sensor circuit circuit malfunction circuit  Engine coolant temp . sensor O  EC U Engine coolant temp . 20 min . or more after starting engine, engin e P0116 circuitrange/ ON coolant temp . sensor value is 30°C (86°F) of  Engine coolant temp . sensor 0 performance problem less  Coolant syste m (2 trip detection logic)' 3 + 1 * 2 *3 "ON" displayed in the diagnosis mode column indicates that the "CHECK ENGINE" warning light is lighted up when a malfunction is detected . "0" in the memory column indicates that a diagnostic code is recorded in the ECU memory when a malfunction is detected . Accordingly, output of diagnostic results in normal or test mode is perform- ed with the ignition switch ON . " 2 trip detection logic" ( See page 134) . 140 FAIL-SAFE FUNCTION - Fail-safe Functio n FAIL-SAFE FUNCTIO N FAIL-SAFE FUNCTIO N If the Engine ECU were to continue to control the engine based on faulty signals, other malfunctions could occur in the engine . To prevent such a problem, the fail-safe function of the ECU either relies on the data stored in memory to allow the engine control system to continue operating, or stops the engine if a hazard is anticipated . ® The following table describes the problems which can occur when trouble occurs in the various circuits, and the responses of the fail- safe function . (A circle in the "4A-FE ENGINE" column indicates the provision of the fail-safe function in vehicles equipped with the 4A-FE engine . ) CIRCUITRY WITH 4A-F E ABNORMAL SIGNALS NECESSITY OPERATION ENGIN E If trouble occurs in the ignition system and Fuel injection is stopped . Ignition confirmation ignition cannot take place (the ignitio n 't reach th e confirmation [IGF] signal doesn 0 (IGF) signal circuitry ECU), the catalyst could overheat due t o misfiring . If an open or sho rt circuit occurs in the Fixed (standard) values determine d at the time of starting by the condi - Manifold pressure intake manifold pressure sensor signal tion of the idle contact are used fo r sensor (vacuum circuit ry , the basic injection duration cannot the fuel injection duration and the ig- 0 sensor) (PIM) signal be calculated, resulting in engine stalling or nition timing making engine opera - circuitry inability to start the engine . tion possible . If an open or sho rt circuit occurs in the air Fixed (standard) values determine d flow meter signal circuitry, it becomes at the time of starting or by the condi - Air flow meter (VS , Air impossible to detect the intake air volume tion of the idle contact are used fo r or VG) signal cir- and calculation of the basic injection ig - the fuel injection duration and the ig - cuitry Isome engine duration cannot be done . This results in nition timing making engine opera - models only ) models stalling or inability to sta rt the tion possible . engine . If an open or sho rt circuit occurs in the Values for normal operatio n Throttle position (VTA) thrott le position sensor signal circuit ry , the (standard values) are used . (These Z signal circuit ry (linear ECU detects the throttle valve as being standard values differ depending on 0 type) either fully open or fully closed. As a result, the engine model . ) the engine stalls or runs rough . Since the G1 and G2 signals are used in If only the G1 or only the G2 signal i s cylinder identification and in detecting the still being received, the standar d Engine crankshaft crankshaft angle, if an open or sho rt circuit crankshaft angle can still be judge d angle sensor (G1 and occurs, the engine cannot be controlled, by the remaining G signal . 0 G2) signal circuit ry resulting in engine stalling or inability to sta rt the engine . . 1 2 (Continued on next page ) In previous models, the back-up mode is entered when terminal T is off . There were also some models in which standard values are used for the intake manifold pressure signal if terminal T is connected to the El terminal . Only for models which are equipped with the lean mixture sensor . 145 0 FAIL SAFE FUNCTION - Fail-safe Functio n CIRCUITRY WITH 4A-F E ABNORMAL SIGNALS NECESSITY OPERATION ENGIN E  Water temp . If an open or sho rt circuit occurs in the Values for normal operatio n sensor (THW) water temperature or intake air (standard values) are used . Thes e signal circuit ry temperature signal circuitry the ECU standard values differ depending o n assumes that the temperature is below engine characteristics, but generally ,  Intake air temp . -50°C (-58°F) or higher than 139°C (274°F) . a coolant temperature of 80°C 0 sensor (THA) This results in the air-fuel ratio becoming (176°F) and an intake ai r signal circuit ry too rich or too lean, which results in engine temperature of 20°C (68°F) are used . stalling or the engine running rough . If the cover of the lean mixture sensor Air-fuel ratio feedback correction i s becomes fouled with carbon, the ECU stopped . Lean mixture sensor cannot detect the correct oxygen 0 . (LS) signal circuit ry concentration in the exhaust gas, so i t cannot keep the air-fuel ratio at the optimal level .  Knock sensor If an open or sho rt circuit occurs in the The corrective retard angle is set t o (KNK) signal knock signal circuitry, or if trouble occurs in the maximum value . circuitry the knock control system inside the ECU , whether knocking occurs or not, ignitio n  Knock control timing retard control will not be carried out system by the knock control system . This coul d result in damage to the engine . If an open or sho rt circuit occurs in the HAC Values for normal operatio n High-altitude sensor signal circuitry, the high-altitude (standard values) are used . Th e compensatior sensor compensation correction will be either the standard atmospheric pressur e (HAC) signal circuit ry maximum or the minimum value . This will value is 101 kPa (60 mmHg, 29 . 9 cause the engine to run poorly or reduce in.Hg) . drivability . Turbocharging Abnormal increases in the turbocharging Fail-safe stops engine by stoppin g pressure (PIM) signal pressure or intake air volume, as well as fuel injection . circuit ry other factors, may cause damage to th e turbocharger or engine . Transmission control If trouble occurs in the microprocessor for Torque control correction (See pag e signal transmission control, the transmission will 96) by the ESA is stopped . not operate properly . If the amount of coolant supplied to the The ignition timing is retarded by 2° . intercooler is insufficient, its coolin g Intercooler ECU (WIN) capacity will drop . This will cause th e signal circuitry temperature of air taken into the cylinders to rise. As a result, the temperature of th e gas inside the combustion chamber wil l rise even higher, making it easy fo r knocking to occur . *Only for models which are equipped with the lean mixture sensor . 146 BACK-UP FUNCTION - Back-up function BACK-UP FUNCTIO N BACK-UP FUNCTIO N The back-up function is a system which switches to the back-up IC for fixed signal control* if trouble occurs with the microprocessor inside the ECU . This allows the vehicle to continue operating, though it assures the continuation of l Engine ECU Back-up I C STA:::= IDL Malfunction monitor only basic functions ; normal performance cannot be maintained . *Control by the back-up IC in which the IC uses preprogrammed data to control the ignition timing and fuel injection duration . Microprocessor *Injectio n signal 0- O Various signal s *Ignitio n timing signal IGT Xn k 1 o,zo -&- OPERATIO N The ECU switches to the back-up mode when the microprocessor stops outputting the ignition tim- ing (IGT) signal . When the ECU switches to the back-up mode, fix- ed values* are substituted for fuel injection dura- tion and ignition timing and as a result, engine operation is maintained . The back-up IC sets the fixed values* according to the condition of the STA signal and the idle contact . At the same time, it lights the "CHECK ENGINE" lamp to inform the driver . (Codes are not output in this case, however . ) *These values differ depending on the engine model . In addition, on some recent models, when the back-up mode is entered, the engine is stopped by interrupting fuel injection . /__ NOT E In the case of conventional D-type EFI, when the intake manifold pressure (PIM) signal was open or short circuited, the microprocessor for- cibly switched to the back-up mode by interrup- ting the ignition timing (IGT) signal. More recently, however, fixed values for fuel injec- tion duration and ignition timing are contained within the microprocessor . As a result, when a problem like that described above occurs, the microprocessor controls the engine with a fail safe function . 147 8b l OW3W TROUBLESHOOTING - General TROUBLESHOOTING GENERAL The TCCS engine control system is a very complicated system requiring a high level of technical knowledge and expertise to troubleshoot successfully . However, the basics of troubleshooting are the same whether an engine is equipped with a TCCS engine control system or it is a carbureted engine. In particular, you must look for:  An appropriate air-fuel mixture  A high compression pressure  Correct ignition timing and powerful sparks Making effective use of the diagnostic system ( See page 131) and taking into careful consideration the three items mentioned above will eliminate the complexities involved in troubleshooting vehicles with TCCS . It is also ve ry important to follow the correct procedures at all times . This section explains the general procedures and concepts involved in troubleshooting, from the point when the vehicle is brought into the se rvice shop until the trouble is found and repaired and the confirmation test performed . For correct troubleshooting procedures for a particular engine, see the Repair Manual for that engine model . 149 TROUBLESHOOTING - How to Carry Out Troubleshooting HOW TO CARRY OUT TROUBLESHOOTIN G The ideal procedure for troubleshooting and how to carry out the necessary repairs are explained below . C VEHICLE BROUGHT INTO SERVICE SHO P 1 PRE-DIAGNOSTIC QUESTIONING Page 15 2 2 CHECKING AND CLEARING DIAGNOSTIC CODES (PRECHECK) Page 15 9 SETTING DIAGNOSTIC TEST MODE (For vehicles equipped with Page 161 diagnostic test mode only ) 4 Problem occurs . 6 Problem does not occur . SYMPTOM SIMULATIO N 5 ,a CHECKING DIAGNOSTIC CODE Page 15 9 Normal code ~ Malfunction cod e 9 [L ~ 7 INSPECTION OF COMPONENTS// Page 17 1 BASIC INSPECTION Page 167 CIRCUIT INSPECTIO N i3 DIAGNOSTIC CODES Page 13 8 SYMPTOM CHART Page 15 4 V IDENTIFICATION OF PROBLEM 13 14 Page 163 7 1 2 ~ SYMPTOM SIMULATION Page 16 3 ADJUSTMENT AND/OR REPAIR Page 17 1 ,a CLEARING DIAGNOSTIC CODES Page 16 2 `c~ 15 CONFIRMATION TEST ,a C END SYMPTOM CONFIRMATION OHP 95 150 TROUBLESHOOTING - How to Carry Out Troubleshooting PRE-DIAGNOSTIC QUESTIONIN G Refering to the Pre-diagnostic Questioning Checksheet, ask the customer about the problem in as much detail as possible . CHECKING AND CLEARING DIAGNOSTIC CODES (PRECHECK ) Before confirming the symptoms, check the diagnostic code in the normal mode and make a note of any malfunction codes dis- played, then clear the codes . 3 SETTING DIAGNOSTIC TEST MOD E (for vehicles equipped with diagnostic test mode . ) In order to find the cause of the problem more quickly, set the system in the diagnostic test mode . SYMPTOM CONFIRMATIO N Confirm the symptoms of the problem . SYMPTOM SIMULATION If the symptoms do not reappear, use the symptom simulation method to reproduce them . CHECKING DIAGNOSTIC COD E Check the diagnostic codes. If the normal code is output, proceed to step ❑ ~ . If a mal- function code is output, proceed to ste p BASIC INSPECTION 8 Carry out a basic inspection, such as an ig- nition spark check, fuel pressure check, etc . 8 DIAGNOSTIC CODE S If a malfunction code was output in step 6 check the trouble area indicated by the diagnostic code chart . 1 1 1 2 13 15 SYMPTOM CHART If a trouble was not confirmed in step ❑ perform troubleshooting according to the in- spection items in the symptom chart . CIRCUIT INSPECTIO N Proceed with the diagnosis of each circuit between the ECU and the component in accordance with the inspection items confirmed in step ® or step ❑ . Determine whether the cause of the trouble is in the sensors, the actuators, the wire harness or connector, or the ECU . INSPECTION OF COMPONENTS Inspect the problematic components . SYMPTOM SIMULATIO N If the cause of the trouble is momentary (intermittent) interruptions or shorts, pull gently on the wire harness, connectors, and terminals, and shake them gently to isolate the place where the trouble is occurring due to poor contact . ADJUSTMENT AND/OR REPAI R After the cause of the trouble is located, per- form the necessary adjustment or repair . CLEARING DIAGNOSTIC CODES Clear the diagnostic codes . CONFIRMATION TEST After completing the adjustment or repairs, check to see whether the trouble has been eliminated, and perform a test drive to make sure the entire engine control system is operating normally and that the diagnostic code displayed is the normal code . 151 TROUBLESHOOTING - Pre-diagnostic Questionin g PRE-DIAGNOSTIC QUESTIONING (PDQ ) When carrying out troubleshooting, it is impor-  Who noticed the problem ? tant that the technician remember to confirm the - With whom the problem most commonly symptoms of the problem accurately and objec- occur s tively, without preconceptions . (This means, for  What? example, not to just guess about the cause of the problem, no matter how much experience - Vehicle mode l - System in which problem has occurred the technician is basing his judgement on, but t o carry out the troubleshooting step by step, ac-  When? cording to the directions given here .) - Date(s) No matter how experienced the technician, if -Time(s) troubleshooting is attempted before the - Frequency of occurrence symptoms have been confirmed, repairs will fai l or a mistaken judgment will lead to the wrong  Where 7 repairs being performed . - Type of road/terrain As long as the symptoms of the problem are  How? Under what conditions? manifesting themselves at the time the vehicle - Engine running conditions is brought into the service shop, they can be - Driving conditions confirmed right away. However, when the - Weathe r symptoms fail to manifest themselves, the  Why did customer bring vehicle in? technician must deliberately try to reproduce - Symptoms them. For example, a problem that occurs onl y when the vehicle is cold or the occurrence of A sample of a PDQ Checksheet is shown on the vibration from the road surface during driving following page . cannot be confirmed when the engine is warmed up or while the vehicle is sitting still, because the conditions under which the trouble occurred cannot be reproduced under such circumstances . Therefore, when attempting to ascertain what the symptoms are, it is extremely important to ask the customer about the problem and the conditions under which they occurred . IMPORTANT POINTS IN PD Q The six items shown below are especially impor- tant points to remember when carrying out Pre- diagnostic Questioning . Information on past problems (even if they are thought to be unrelated to the present problem) and the repair history of the vehicle will also help in many cases, so as much information as possible should be gathered and its relationship with the symptoms should be correctly ascertained for reference in troubleshooting . 152 TROUBLESHOOTING - Pre-diagnostic Questioning PRE-DIAGNOSTIC QUESTIONING CHECKSHEET Inspector's Name : Customer's Model and model yea r name Driver's name Frame no . Date vehicle Engine mode l brought in License no. Odometer reading km mile s ❑ Engine does ❑ Engine does not crank ❑ No initial combustion ❑ Incomplete combustio n not start ❑ Difficult to ❑ Engine cranks slowl y start ❑ Othe r E ❑ Poor idling ❑ No fast idle ❑ Idling speed : ❑ High ❑ Low ( rpm ) ❑ Rough idling ❑ Othe r C L E ❑ Poor ❑ Hesitation ❑ Backfiring ❑ Afterfiring (muffler explosions) ❑ Surgin g driveability ❑ Knocking ❑ Other ❑ Soon after starting ❑ After accelerator pedal is depresse d ❑ Engine stalls ❑ After accelerator pedal is released ❑ During A/C operatio n ❑ Shifting from "N" to "D" ❑ Other ❑ Others Datels) of problem occurrence Frequency of problem ❑ Constant ❑ Sometimes (times per day/month) ❑ Once only occurrence ❑ Other Weather ❑ Clear ❑ Cloudy ❑ Rainy ❑ Snowy ❑ Various/othe r o m Outdoor ❑ Hot ❑ Warm ❑ Cool ❑ Cold (approx. _°C /_°F ) ~ temperatur e E Place /road ❑ Highway ❑ Suburbs ❑ Inner city ❑ Uphill ❑ Downhil l W ~ conditions ❑ Rough road ❑ Other N V C « E Engine temp . ❑ Cold ❑ Warming up ❑ Normal ❑ Other e ~ o ❑ Sta rting ❑ Just after starting ❑ Idling ❑ Racin g cg a Engine operation ❑ Driving ❑ Constant speed ❑ Acceleration ❑ Deceleratio n ❑ Other Condition of "CHECK ENGINE" lamp ❑ Always on ❑ Flickers ❑ Does not light u p 1st time ( precheck) ❑ Normal code ❑ Malfunction code(s) ( Diagnostic code check 2nd El Normal mode ❑ Normal code El Malfunction code(s) ( time ❑ Test mode 153 SYMPTOM CHART TROUBLESHOOTING - Symptom Chart If no malfunction code is output and the problem cannot be confirmed by a basic inspection, pro- ceed to this cha rt and perform troubleshooting . This is a cha rt of problem symptoms which was prepared based on the 4A-FE engine (Sep ., 1989)* . It is meant only to serve as a means of familiarizing you with basic troubleshooting pro- cedures, and is by no means complete . For actual troubleshooting procedures, refer to the repair manual for the appropriate engine . *Except for models which are equipped with the lean mixture sensor . REFERENCE 1 . The ECU is not included in the list o f POSSIBLE CAUSES . However, if all other components and circuits check out okay, it can be concluded that the ECU is probably at fault . 2 . Be sure to also check the wiring harness and connectors when checking the parts themselves . 3. One reason why some problems may not be detected by the diagnostic system even when the symptoms do recur is that they may have occurred outside the diagnostic system's range of abnormality detection or the problem not covered by the diagnostic system may have occurred . (See page 132 . ) SYMPTOM POSSIBLE CAUS E SYSTEM COMPONENT PART TYPE OF TROUBLE Power su l s stem Ignition switch Poor contact pp y y EFI main relay Won't go o n Circuit opening relay Won't go o n Fuel pump Won't operate Fuel system Injectors Won't inject Pressure regulator Fuel pressure too low Engine does No initial Fuel filter, fuel line Clogged not start combustion Cold sta rt s stem Cold start injector Won't inject y Start injector time SW Won't go on, stays o n Igniter Ignition system Ignition coil No sparking Distributo r Electronic contro l system Distributo r (G and NE signals) G and NE signals no t output 154 SYMPTOM Engine does not start There is combustion but engine does not start (incomplete combustion ) Starting is difficult Col d Hot Always TROUBLESHOOTING - Symptom Chart SYSTEM Fuel syste m Cold sta rt system POSSIBLE CAUS E COMPONENT PART Circuit opening rela y Injectors Pressure regulato r Fuel filter, fuel lin e Cold sta rt injector Sta rt injector time SW Ignition syste m Air induction system Electronic control system Cold start syste m Air induction syste m Electronic control system Fuel syste m Cold start system Air induction syste m Fuel syste m Cold start syste m Ignition system Spark plug s Air hose s Air valv e Manifold pressure sensor (vacuum sensor ) Water temp . sensor Cold start injector Start injector time SW ISC valv e Air valv e Water temp . sensor Intake air temp. senso r Injectors Pressure regulato r Cold sta rt injector Air valv e Circuit opening relay Fuel filter, fuel lin e Cold start injector Spark plugs TYPE OF TROUBLE Won't go on Leakage, won't inject, inject continuousl y Fuel pressure too low Clogge d Won't inject Won't go on Misfire Leakage Won't open fully, won't open at al l Voltage or resistance are incorrect, open or short circuit Won't inject Won't go o n Won't open fully, won't open at al l Open or sho rt circuit Leakage Fuel pressure too low Leakage Won't open fully STA circuit won't go o n Clogging Leakage Fouled 155 ❑ +~ TROUBLESHOOTING - Symptom Chart POSSIBLE CAUS E SYMPTOM SYSTEM COMPONENT PART TYPE OF TROUBLE Ai induction s stem ISC valve Won't open fully, r y Air valve won't open at al l t id l N fas e o Electronic control Water temp. sensor Open or sho rt circuit system Cold sta rt system Cold sta rt injector Leakin g Throttle body Won't close full y Air induction system ISC valve en continuous l Sta s o y y p Idle speed too Air valve high Manifold pressure sensor (vacuum sensor) Voltage or resistanc e are incorrect Electronic control Water temp . sensor system Throttle position sensor Idle contact won't go on Air conditioner switch Stays on continuousl y Air induction system ISC valve Stays close d Rough idling Manifold pressure Voltage or resistance Idle speed too sensor (vacuum sensor) are incorrect, open o r low Electronic control short circuit system Neutral sta rt switch Won't o o n g Air conditioner switc h Fuel pump Malfunctionin g Fuel s stem Injectors Won't inject y Pressure regulator Malfunctioning Fuel filter, fuel line Clogge d Throttle body Air suctio n Air induction system ISC valve Malfunctionin g Air valv e Unstable idling Igniter Malfunctionin g Ignition system Ignition coil ( poor contact) Spark plugs Misfir e Manifold pressure Malfunctioning Electronic control sensor (vacuum sensor ) system Thrott le position sensor Idle contact won't go o n Oxygen (02) sensor Malfunctionin g 156 TROUBLESHOOTING - Symptom Chart SYMPTOM POSSIBLE CAUS E SYSTEM COMPONENT PART TYPE OF TROUBLE Fuel pump Drop in flow volum e l t F Injectors Drop in injection volum e em ue sys Pressure regulator Fuel pressure too low Fuel filter, fuel line Clogged Igniter Malfunctionin g Hesitates during Ignition system Ignition coil (poor contact ) acceleration Spark plugs Misfire Manifold pressure sensor (vacuum sensor) e or resistanc e Volta Electronic control Water temp. sensor g are incorrect, open o r system Intake air temp. sensor sho rt circuit Throttle position senso r Oxygen (02) sensor Malfunctionin g Fuel pump Drop in flow volum e l F t Injectors Drop in injection volum e e m ue sys Pressure regulator Fuel pressure too lo w Poor drivability Fuel filter, fuel line Clogged Igniter Malfunctionin g Ignition system Ignition coil (poor contact ) Backfiring Spark plugs Misfire Manifold pressure sensor (vacuum sensor) Electronic control Water temp . sensor Voltage or resistance system Intake air temp. sensor are incorrect Throttle position senso r Oxygen (02) sensor Malfunctionin g Fuel system Injectors Leakage Cold sta rt system Cold sta rt injector Leakage, inject s continuously Sta rt injector time SW Stays on continuousl y Afterfiring (muffler Manifold pressure sensor (vacuum sensor) Voltage or resistanc e explosions) Electronic control Water temp . sensor are incorrect system Intake air temp. sensor Throttle position sensor Idle contact won't go o n Oxygen (02) sensor Malfunctioning 157 0 TROUBLESHOOTING - Symptom Chart POSSIBLE CAUSE SYMPTOM SYSTEM COMPONENT PART TYPE OF TROUBLE Fuel pump Drop in flow volum e Injectors Drop in injection volum e Fuel s stem y Pressure regulator Fuel pressure too low Insufficient Fuel filter, fuel line Clogged Poor drivability power Ignition system Spark plugs Misfir e Manifold pressure Electronic control sensor (vacuum sensor) Voltage or resistanc e system Water temp. sensor are incorrect Throttle position sensor PSW signal not outpu t Circuit opening relay FC circuit won't go o n Fuel system Injectors Leaking, won't inject , Engine stalls injects continuousl y shortly after sta rt ing Cold start injector Leakage, inject s Cold sta rt system continuousl y Start injector time SW Stays on continuously Engine stalls Manifold pressure when accele- Electronic control sensor (vacuum sensor) Voltage or resistanc e rator pedal is system are incorrect Engine stalling depressed Water temp. senso r Throttle position sensor Malfunctioning Air induction s stem Engine stalls y when accele- Air valve Stays closed rator pedal is Electronic control Manifold pressure Voltage or resistanc e released system sensor (vacuum sensor) are incorrect Engine stalls Air induction system ISC valve Malfunctioning when ai r conditioner i s switched on Electronic control Air conditioner switch Signal not output system Engine stalls Air induction system ISC valve Malfunctionin g when ATM i s shifted fro m "N" to "D" Electronic control Neutral sta rt switch Signal not outpu t position syste m 158 CHECKING AND CLEARING DIAGNOSTIC CODES ® CHECKING AND CLEARING DIAGNOSTIC CODE S OBJECTIVE : To learn how to check and clear diagnostic codes . PREPARATION : SST 09843-18020 Diagnosis check wire APPLICABLE ENGINE : 4A-FE ( Sep ., 1989 ) /--- n~r~nu M ~~ -- This section basically covers the 4A-FE engine . However, since the TDCL and test mode function in the diagnosis system are not provided in the 4A-FE engine, the procedures and illustrations related to these items are explained using the 1 UZ-FE (Dec ., 1989) engine . C~3 CHECK ENGIN E CHECK Check connecto r SST or TE1 El 0 TDC L 1L SST El TE1 "CHECK ENGINE" LAMP CHEC K (a) The "CHECK ENGINE" lamp should come on when the ignition switch is turned on (engine not running) . (b) When the engine is started, the "CHECK ENGINE" lamp should go off. If the light remains on, it indicates that the diagnostic system has detected a malfunction or abnormality in the diagnostic system . OUTPUT OF DIAGNOSTIC CODE S 1 . NORMAL MODE To output the diagnostic codes, proceed as follows : (a) Initial conditions :  Battery voltage at 11 V or higher  Transmission in "N" rang e  Ail accessories switched off (b) Turn the ignition switch on . (c) Using the SST, connect terminal T or TE1 with terminal El of the check connector or the TDCL . SST 09843-18020 159 n CHECKING AND CLEARING DIAGNOSTIC CODE S CHECK ENGINE~ CHECK ~ ~~ 1 sec O n Of f 0.5 sec 1 .5 se c Start 4.5 sec 2 .5 4.5 sec , ~ ~lnsec ~ ~ Off OI I2'eC u u Repea t Code 12 Code 3 1 One cycl e SST 160 (d) Read the diagnostic code as indicated by the number of flashes of the "CHECK ENGINE" lamp . DIAGNOSTIC CODE S (1) Normal code indicatio n  The lamp will alternately blink on and off 2 times per second . (2) Malfunction code indicatio n As an example, the blinking patterns for codes 12 and 31 are as shown in the illustration at left .  The lamp will blink the number of times equal to the malfunction code . It will go off for a longer period as follows : ri Once between the first and second digit of the same code, 1 .5 seconds . `2) Once between one code and the next code, 2.5 seconds . 3i Once between all malfunction codes, 4 .5 seconds . NOTE :  The diagnostic code series will be repeated a s long as check connector terminals T or TE1 and E1 are connected .  In the event of a number of malfunction codes, indication will begin from the small value and continue in order to the larger value (s) .  When the automatic transmission is in the "D", "2", "L" or "R" range, or when the air condi- tioner is on, or when the accelerator pedal is depressed, code "51" (switch condition signal) will be output, but this is normal . (e ) After the diagnostic code check, remove the SST from the check connector or the TDCL . SST 09843-18020 SST 0.13 sec CHECKING AND CLEARING DIAGNOSTIC CODE S 0~~~~~~ h N I I El TE2 l u 2. TEST MOD E To output the diagnostic codes, proceed as follows : (a) Initial conditions :  Batt e ry voltage at 11 volts or highe r  Throttle valve fully closed (idle contact closed)  Transmission in "N" rang e  All accessories switched off (b) Turn the ignition switch off. (c) Using the SST, connect terminal TE2 with terminal El of the TDCL . SST 09843-1802 0 (d) Turn the ignition switch on . NOTE : To confirm that the test mode is operating, see whether the "CHECK ENGINE" lamp blinks when the ignition switch is turned on . This blinking cycle is faster than blinking cycle of normal code . (e) Start the engine . (f) Simulate the conditions of the malfunction described by the customer . If the diagnostic system detects a malfunction, the "CHECK ENGINE" lamp will go on . (g) After performing a road test, connect terminal TE1 with terminal El of the TDCL using the SST . SST 09843-1802 0 (h) Read the diagnostic code as indicated by the number of times the "CHECK ENGINE" lamp blinks . NOTE : The method used to read the diagnostic code is the same as in the normal mode . (i) After completing this check, remove the SSTs from the TDCL . SST 09843-18020 NOTE :  The test mode will not start if terminals TE2 an d El are connected after the ignition switch is turned on .  If the engine is not cranked, diag . code "43" (starter signal) will be output, but this is normal .  When the automatic transmission is in the "D" , "2", "L" or "R" range, or when the air con- ditioner is on, or when the accelerator pedal is depressed, code "51" (switch condition signal) will be output, but this is normal . 161 STOP (1 5A) CHECKING AND CLEARING DIAGNOSTIC CODE S CLEARING DIAGNOSTIC COD E (a) After the trouble is repaired, the diagnostic code retained in memory by the Engine ECU must be cleared by removing the STOP (15 A) fuse or EFI (15 A) fuse for 10 seconds or longer, depending on the ambient temperature (the lower the temperature, the longer the fuse must be left out) with the ignition switch off . NOTE :  Clearing the memory can also be done by removing the ba ttery cable from the negative terminal, but in this case other memo ry systems (radio, clock, etc .) will also be cleare d  If it is necessa ry to work on engine components requiring removal of the cable from the battery terminal, a check must first be made to see if any diagnostic codes have been recorded . (b) After clearing the memory, pe rform a road test to confirm that a "normal" code can now be read . If the same diagnostic code as before appears, it indicates that the trouble has not been completely remedied . 162 SYMPTOM SIMULATION SYMPTOM SIMULATIO N The most difficult problems in troubleshooting are intermittent problems : that is, problems about which the customer has a complaint, but which do not occur or cannot be comfirmed in the service shop . Intermittent problems often include complaints about the "CHECK ENGINE" lamp going on and off erratically . To ensure accurate diagnosis of such problems, ask the customer to provide as much information as possible . To do this, question the customer closely about the problem, using the Pre-diagnostic Questioning Checksheet, then try to reproduce the problem on the customer's vehicle . The symptom simulation methods (applying vibration, heat, or humidity) described below are effective ways of reproducing the symptoms for problems of this nature . OBJECTIVE To learn how to reproduce intermitt ent problems PREPARATIO N APPLICABLE ENGIN E 1 Terminals have sprea d VIBRATION METHOD: When vibration seems to be the major cause . CONNECTORS Gently shake the connectors vertically and hori- zontally and pull on them : (a) Are they loose ? (b) Does the wire harness have enough slack ? Watch especially for :  Dirty terminal s  Loose contact due to spreading of terminals 163 Wt SYMPTOM SIMULATION VIBRATION METHOD (cont'd) : When vibration seems to be the major cause . WIRE HARNES S Gently wiggle the wire harness vertically an d ~ r horizontally. Connector joints and places where wir e harnesses pass through the body are the major area s to be checked . Gently wiggl e Gently tap PARTS AND SENSORS Gently tap the part or sensor in question with you r finger . NOTE R b h l i : emem er t at app y ng too much shock to a J~~ JJ l relay may cause it to open, making it appear that it i s the relay that is at fault when there is really nothin g wrong with it at all . ::2] HEAT METHOD : When the malfunction seems to occur when the suspec t area is heated . Using a hair dryer, heat the component that is the likely cause of the malfunction . Malfunc- tions NOTICE : D h °C  o not eat any component to more than 60 (140°F) ( temperature limit at which the componen t can be safely touched with the hand) .  Never open an ECU and apply heat directly to th e parts inside it . 3 WATER SPRAY METHOD : When the malfunction seems to occur on a rainy day or under conditions of high humidity . Change the temperature and ambient humidity b y spraying water onto the vehicle . NOTICE :  Never spray water directly into the engin e compartment; spray it onto the front of the radiato r through the grill .  Never let water come in direct contact wit h electronic components . NOTE :  If a vehicle is subject to water leakage, the leaking water may get into an ECU . When testing a vehicl e with a water leakage problem, special caution must be used . 164 SYMPTOM SIMULATION ® 4 OTHER : When a malfunction seems to occur due to excessive electrical loads . Switch on all electrical loads especially loads that On draw a heavy current, such as the heater blower, hea d I i lamps, rear window defogger, etc . Irv, ,-~,:.--- - .=~~`_,? 165 W BASIC INSPECTIO N BASIC INSPECTIO N When the "normal" code is displayed during the diagnostic code check, troubleshooting should be performed in the correct order for all possible circuits considered to be the causes of the problems . NO ) Go to ste p OBJECTIVE . To learn how to carry out basic inspection of the engine . PREPARATIONS . SST 09843-18020 Diagnosis check wire  Engine tune-up tester (tachometer, timing light) APPLICABLE ENGINE : 4A-FE* (Sep ., 1989 ) *Except Carina 11 (AT 17 1) with lean mixture senso r 1 Is battery voltage 11 V or more when engine is stopped ? NO j Charge or replace battery . 2 Does engine crank? NO ) Go to Symptom Cha rt (see page 154) . 3 0 0 Visually check to see whether the air cleane r Does engine sta rt? Check air filter . NOTE In many cases, carrying out the basic engine check shown in the following flow chart will allow you to locate the cause of the problem quickly and efficiently . For this reason, it is essential to perform this inspection before troubleshooting engine problems . 8 Remove the air filter . element is excessively dirty, oily or damaged . If necessary, clean the element with compressed air: first blow from the inside thoroughly, then blow off the outside of the element . N G ~ Replace air cleaner element . Procedure 0 Check or inspectio n 167 BASIC INSPECTIO N 5 Is air leaking into air intake system? Check idle speed . Tachometer m Check for air leaking into the air intake system . If the engine oil dipstick, oil filler cap or PCV hose, etc . is loose or missing, air can leak into the air intake system, causing the air-fuel mixture to become too lean . No air leaking into the air intake system between the air flow meter and the cylinder head . N G Repair air leakage . ( 1) Shift the transmission into the " N" range . (2) Warm up the engine to its normal operating temperature . (3) Switch off all accessories . (4) Switch off the air conditioner . (5) Connect a tachometer test probe to the IG e terminal of the check connector . 0 Check the idle speed . O K NO 1I LE Idle speed: 800 rpm (cooling fan off )  NEVER allow the tachometer test probe to touch ground as it could result in damage to the igniter and/or ignition coil .  As some tachometers are not compatible with this ignition system, we recommend that you confirm the compatibility of your unit before use . N G Adjust idle speed . 7 Check ignition timing . ~ (1) Connect the timing light to the engine . ® (2) Run the engine at an idle. SST~~ (3) Using the SST, connect terminal TE1 wit h El terminal El of the check connector . SST 09843-1802 0 TE1* Check co _ nnecto 168 BASIC INSPECTIO N 7 Check ignition timing (cont'd) . © Check the ignition timing using a timing light . m Ignition timing : 10° BTDC (engine idling ) Transmission in the "N" range . Pr ~ ~ r ~~'~ . TI ✓ ~ .d_ , L✓ , ' ~ iy FURTHER CHECK 0 Disconnect the SST . SST SST 09843-18020 0 Use a timing light to check whether the ignitio n timing advances properly . Ignition timing: the timing mark moves no more than 5° on each side of the 10° mark. Transmission in the "N" range . OK NG Adjust ignition timing . Go to Symptom Chart (See page 154) . 169 BASIC INSPECTION W 8 Check fuel pressure . ~ (1) Be sure that there is enough fuel in th e tank . ~ (2) Turn the ignition switch on . SST (3) Using the SST, connect terminal +B wit h o p 6E6i terminal FP of the check connector . SST 09 3 FP + g 84 -1802 0 '- 0 Check if there is pressure in the hose from the Check fuel filter by pinching the hose with you r connector fingers . ~ You should hear the sound of fuel passin g through the fuel return hose . M3 Fuel pressure can be felt . ~ ~ OK NG Repair EFI system . (See Step 2, vol . 5, "EFI" . ) Check for sparks . Repair ignition system . (See Step 2, vol. 3~ N G "Ignition System" . ) Go to Symptom Cha rt (See page 154) . 170 W INSPECTION AND ADJUSTMENT - Genera l INSPECTION AND ADJUSTMEN T GENERAL In this section, the basic inspection and adjustment methods for the major items indicated in the following table for the 4A-FE engine are explained . (Note that inspection and adjustment methods for items with a circle in the "STEP 2, EFI" column in the table have already been explained in Step 2, vol. 5("EFI"], based on the 1G-FE engine, so they are not included in this Training Manual . ) SPECIFICATION FOR 4A-FE ENGINE (As of Mar., 1991 ) ? COROLLA (AE 9#) CELICA (AT 180) ~AT NA ; i INSPECTION AND ADJUSTMENT ITEMS z a C C LU u) Q = d F U W I Q Z) = QF a # 0 N ~ ~LL " LL Q 7 V * I (7 W U W o a LL Q N a Z) U - L L 6 a =i U U W ~ U J > W? w C14 H U) Idle speed and idle mixture 172 0 0 0 0 0 0 0 0 0 0 0 Manifold pressure sensor (vacuum sensor) 175 0 0 0 0 0 0 0 0 0 0 Air flow meter Vane type - 0 Throttle positio n d On-off type - 0 0 0 0 0 0 0 0 0 0 sensor an throttle body Linear type 177 0 Distributor G and NE signals 180 0 0 0 0 0 0 0 0 0 0 Water temperature sensor - 0 0 0 0 0 0 0 0 0 0 0 Intake air temperature sensor 181 0 0 0 0 0 0 0 0 0 0 Feedback correction Oxygen sensor (O2 sensor) 182 0 0 0 0 0 0 0 0 Lean mixture sensor 183 0 Variable resistor 184 0 Fuel pump operation - 0 0 0 0 0 0 0 0 0 0 0 Fuel pressure - 0 0 0 0 0 0 0 0 0 0 0 Injector operation - 0 0 0 0 0 0 0 0 0 0 0 Injector injection volume - 0 0 0 0 0 0 0 0 0 0 0 Cold sta rt injector - 0 0 0 0 0 0 0 0 0 Cold sta rt injector injection volume - 0 0 0 0 0 0 0 0 0 Start injector time switch - 0 0 0 0 0 0 0 0 0 Air valve - 0 0 0 0 0 0 0 0 0 0 0 EFI main relay - 0 0 0 0 0 0 0 0 0 0 0 Circuit opening relay - 0 0 0 0 0 0 0 0 0 0 O ISC valve Duty control ACV type 186 0 0 0 0 0 0 0 0 0 0 * 1 European specification models ( models w/TWC or OC) *2 Except California specification model s *3 California specification model s *4 General Country specification models Since inspection and adjustment of the idle speed and idle mixture differ depending on the vehicle model or specifications, these are included in this manual . For inspection and adjustment methods for items not included in the following table, see the repair manuals for engines equipped with those items . *5 European specification models ( models w/o TWC or OC ) *6 Lean mixture senso r 171 INSPECTION AND ADJUSTMENT - Idle Speed and Idle Mixture IDLE SPEED AND IDLE MIXTUR E OBJECTIVE : To learn the procedure for inspecting and adjusting the idle speed and idle mixture . PREPARATIONS :  SST 09843-18020 Diagnosis check wire  Tachometer  CO meter APPLICABLE ENGINE : 4A-FE ( Sep., 1989 ) 1 . INITIAL CONDITIONS (a) Air cleaner installed (b) All pipes and hoses of the air induction system connected (c) All vacuum lines connected NOTE: All vacuum hoses for the EGR system, etc ., should be properly connected . (d) All accessories switched of f (e) EFI system wiring connectors securely connected (f) Ignition timing correctly set (g) Transmission in "N" range 2. WARM UP ENGIN E Allow the engine to reach its normal operating temperature . 3. CONNECT TACHOMETE R Connect the test probe of a tachometer to the IG ~ terminal of the check connector . NOTICE :  NEVER allow the tachometer terminal to touch ground as it could result in damage to the igniter and/or ignition coil .  As some tachometers are not compatible with this ignition system, we recommend that you confirm the compatibility of your unit before use . 4. CHECK AIR VALVE OPERATION 5. CHECK AND ADJUST IDLE SPEE D (a) Race the engine at 2,500 rpm for about 90 seconds . (b) Using the SST, connect terminal T or TE1 with terminal El of the check connector . SST 09843-18020 (c) Check the idle speed . Idle speed ( cooling fan off) : 2WD (Federal U.S. and Canada) 700 rpm Others 800 rp m If not as specified, adjust the idle speed by turning the idle speed adjusting screw . NOTE: For Federal U .S. and Canada 2WD manual transmission vehicles with the Daytime Running Light System, the idle speed should rise to 800 rpm . 172 W INSPECTION AND ADJUSTMENT - Idle Speed and Idle Mixtur e (d) Remove the tachometer and SST . SST 09843-1802 0 6. ADJUST IDLE MIXTURE (MODELS WITHOUT TWC) NOTICE: It is usually not necessa ry to adjust the idle mixture in most models, provided that the vehicle is in good condition . However, if it does become necessa ry to do so, always use a CO meter. If a CO meter is not available, it is best not to attempt to adjust the idle mixture if at all possible . (a) Race the engine at 2,500 rpm for approx. 90 seconds . (b) Insert a testing probe at least 40 cm (1 .3 ft) into the tailpipe . (c) Measure the CO concentration for 1 to 3 minutes . Idle CO concentration : 1 .5 ± 0.5 % (cooling fan off ) If the CO concentration is not as specified, adjust the idle mixture by turning the idle mixture adjusting screw in the variable resistor .  If the concentration is within the specification, this adjustment is complete . NOTE: Always check the idle speed after turning the idle mixture adjusting screw . If it is incorrect, repeat steps 5 and 6 . 173 INSPECTION AND ADJUSTMENT - Manifold Pressure Sensor (Vacuum Sensor ) MANIFOLD PRESSURE SENSOR (VACUUM SENSOR) OBJECTIVE To learn the procedure for inspecting the manifold pressure sensor (vacuum sensor) . PREPARATIONS . Voltmeter (also called "circuit tester" or "multi-tester")  Mityvac ( hand-held vacuum pump ) APPLICABLE ENGINE : 4A-FE* (Sep ., 1989 ) *Except Carina 11 (AT 171) with lean mixture senso r Vacuum chamber E2 PIM VC ~ From intake manifold INSPECTION OF MANIFOLD PRESSURE SENSOR (VACUUM SENSOR ) 1 . CHECK POWER SOURCE VOLTAGE OF MANIFOLD PRESSURE SENSO R (a) Disconnect the manifold pressure sensor connector . (b) Turn the ignition switch on . (c) Using a voltmeter, measure the voltage between terminals VC and E2 of the manifold pressure sensor connector . Voltage: 4 - 6 V 2. CHECK POWER OUTPUT OF MANIFOLD PRESSURE SENSO R (a) Turn the ignition switch on . (b) Disconnect the vacuum hose at the intake chamber side . (c) Connect a voltmeter to terminals PIM and E2 of the ECU, and measure and record the output voltage under the ambient atmospheric pressure . (d) Using a Mityvac (hand-held vacuum pump), apply vacuum to the manifold pressure sensor in increments of 13.3 kPa (100 mmHg, 3 .94 in.Hg) until the vacuum reaches 66.7 kPa (500 mmHg, 19 .69 in.Hg) . 175 ® 2WD Voltmeter v O 4WD INSPECTION AND ADJUSTMENT - Manifold Pressure Sensor (Vacuum Sensor ) ECU PIM ~ooooo000 ❑❑ aoooaoooooy~o~ U- E2 ; i mr~dno~ j 11 _ :_]~ ~0 ❑ (e) Measure the voltage drop at each stage . Voltage drop APPLIED 13 .3 26.7 40.0 53.3 66 7 VACUUM . kPa g 10 0 ( 2 0 ( 0 ) 30 ( 1) 40 0 ( ) ( ~ ) \ in.Hg J 3.94 J 7 .8 7 11 .8 15. 5 19 69 Voltage drop (V) 0.3-0 .5 0.7-0 .9 1 .1 -1 .3 1 .5-1 .7 1.9-2. 1 176 INSPECTION AND ADJUSTMENT - Throttle Position Sensor and Throttle Body THROTTLE POSITION SENSOR (LINEAR TYPE) AND THROTTLE BODY OBJECTIVE : To learn the procedure for inspecting and adjusting the throttle position sensor and throttle body . PREPARATIONS : Ohmmeter (also called "circuit tester" or "multi-tester")  Feeler gauge APPLICABLE ENGINE : 4A-FE* (Sep ., 1989 ) *Only for Carina 11 (AT 171) with lean mixture senso r ON-VEHICLE INSPECTION ® 1 . INSPECT THROTTLE BOD Y (a) Check that the throttle linkage moves smoothly . (b) Check for vacuum at the N po rt .  Sta rt the engine .  Check for vacuum with your finger . 177 W INSPECTION AND ADJUSTMENT - Throttle Position Sensor and Throttle Bod y E2 IDL VTA E2 VTA IDL E2 2. INSPECT THROTTLE POSITION SENSOR (a) Disconnect the sensor connector . (b) Insert a feeler gauge between the throttle stop screw and stop lever. (c) Using an ohmmeter, measure the resistance between each terminal . If the resistance is not as specified, adjust or replace the throttle position sensor. CLEARANCE BETWEEN BETWEEN LEVER AND STOP TERMINALS RESISTANCE S2 SCREW mm (in . ) 0(0) VTA - E2 200 - 80 0 0.35 (0.014) IDL- E2 2,300 or less 0.59 (0.023) IDL - E2 Infinit y Throttle valve fully opened y fA-E2 3,300 - 10,00 0 - VC-E2 3,000 - 7,00 0 (d) Reconnect the sensor connector . INSPECTION OF THROTTLE BODY 1 . CLEAN THROTTLE BOD Y (a) Using a soft brush and carburetor cleaner, clean the cast parts . (b) Using compressed air, clean all passages apertures . NOTICE: To prevent damage, do not clean the throttle position sensor . 2. INSPECT THROTTLE BODY VALV E Check that there is no clearance between the throttle stop screw and throttle lever when the throttle valve is fully closed . 3 . INSPECT THROTTLE POSITION SENSOR (See step 2 on "ON-VEHICLE INSPECTION" ) 4. IF NECESSARY, ADJUST THROTTLE POSITION SENSO R (a) Loosen the two set screws of the sensor . 178 INSPECTION AND ADJUSTMENT - Throttle Position Sensor and Throttle Body W (b) Insert a 0.47 mm (0.019 in.) feeler gauge between the throttle stop screw and stop lever. (c) Connect the test probe of an ohmmeter to terminals IDL and E2 of the sensor . (d) Gradually turn the sensor clockwise until the ohmmeter deflects, then secure it with the two screws . (e) Recheck the continuity between terminals IDL and E2 . CLEARANCE BETWEEN LEVER CONTINUITY (IDL - E2 ) AND STOP SCREW mm (in . ) 0.35 (0.014) Continuity 0.59 (0 .023) No continuity 179 INSPECTION AND ADJUSTMENT - Distributo r DISTRIBUTOR (G AND NE SIGNALS ) OBJECTIVE . To learn the procedure for inspecting the distributor (G and NE signals) . PREPARATIONS : Ohmmeter ( also called "circuit tester" or "multi-tester" )  Feeler gauge APPLICABLE ENGINE : 4A-FE* (Sep ., 1989 ) *Except Carina II (AT 171) with lean mixture senso r 1 . INSPECT AIR GAP Using a feeler gauge, measure the gap between the signal timing rotor and the pickup coil projection . Air gap: 0.2 mm ( 0.008 in.) or mor e If the air gap is not as specified, replace the distributor housing . 2. INSPECT SIGNAL GENERATOR (PICKUP COIL) RESISTANC E Using an ohmmeter, measure the resistance between the terminals (G1 and G G, NE and G 6) . Pickup coil resistance (cold) : 185 - 265 S2 If the resistance is not as specified, replace the distributor housing . 180 INSPECTION AND ADJUSTMENT - Intake Air Temperature Senso r INTAKE AIR TEMPERATURE SENSO R OBJECTIVE To learn the procedure for inspecting the intake air temperature sensor . PREPARATION . Ohmmeter ( also called "circuit tester" or "multi-tester" ) APPLICABLE ENGINE 4A-FE (Sep ., 1989 ) Thermistor -20 0 20 40 60 80 100 120 (-4) (32) (68) (104) (140) (176) (212) (248 ) Temperature °C (°F) W INSPECTION OF INTAKE AIR TEMPERATURE SENSO R Using an ohmmeter, measure the resistance between the terminals . Resistance: Refer to the chart above. If the resistance is not as specified, replace the sensor . 181 INSPECTION AND ADJUSTMENT - Feedback Correctio n FEEDBACK CORRECTION OBJECTIVE : To learn how to check feedback correction . PREPARATIONS :  SST 09843-18020 Diagnosis check wir e  Analog type voltmeter ( also called "circuit tester" or "multi-tester") APPLICABLE ENGINE : 4A-FE ( Sep., 1989 ) MODELS W/OXYGEN SENSOR (02 SENSOR) CHECKING FEEDBACK CORRECTIO N (a) Warm up the engine to 80°C (176°F) . (b) Connect a voltmeter to check connector terminals VF or VF1 and E1 . NOTICE: If terminals T or TE7 and E7 are not connected, 0 V, 2.5 V, or 5 V will be output from the VF or VF1 terminal . The meaning of this VF voltage differs depending on the engine . For furt her details, see page 136 . (c) Connect terminal T or TE1 with terminal El of the check connector . SST 09843-18020 (d) Warm up the oxygen sensor to operating temperature by running the engine at 2,500 rpm for about 2 minutes . (e) While maintaining the engine speed at 2,500 rpm, check that the needle of the voltmeter fluctuates eight or more times in 10 seconds . 182 INSPECTION AND ADJUSTMENT - Feedback Correctio n MODELS W/LEAN MIXTURE SENSOR CHECKING FEEDBACK CORRECTIO N (a) Warm up the engine to 80°C (176°F) . (b) Connect a voltmeter to check connector terminals VF or VF1 and El . (c) Connect terminal T or TE1 with terminal El of the check connector. SST 09843-18020 (d) Warm up the lean mixture sensor to operating temperature by running the engine at idle for at least 10 minutes . (e) To start feedback correction, race the engine at 3,500 rpm, then repeat 20 seconds later . (f) While the maintaining engine speed at 1,500 rpm, check the VF terminal voltage . 0 V: Air-fuel ratio feedback correction is taking place 2.5 V or 5 V : Air-fuel ratio feedback correction is not taking place 183 INSPECTION AND ADJUSTMENT - Variable Resisto r VARIABLE RESISTO R OBJECTIVE : To learn the procedure for inspecting the variable resistor. PREPARATION : Volt- and ohmmeter (also called "circuit tester" or "multi-tester") APPLICABLE ENGINE : 4A-FE (Sep ., 1989 ) INSPECTION OF VARIABLE RESISTOR 1 . INSPECT VOLTAGE OF VARIABLE RESISTO R (a) Using a voltmeter, measure the voltage between ECU terminals VC and E2 . Voltage: 4 - 6 V (b) Measure the voltage between ECU terminals VAF and E2 while slowly turning the idle mixture adjusting screw, first fully counterclockwise, then fully clockwise . 184 Voltmeter Ov 0 0 +o 0 E2 -4-,~JIJJC_ii7~C _~i~r_n,r~poo (c) Check that the voltage changes smoothly from 0 V to approx. 5 V . 2 . INSPECT RESISTANCE OF VARIABLE RESISTOR (a) Disconnect the variable resistor connector . (b) Using an ohmmeter, measure the resistance between terminals VC and E2 . Resistance: 4 - 6 kS 2 (c) Turn the idle mixture adjusting screw fully counterclockwise . (d) Connect an ohmmeter to terminals VAF and E2 . Turn the adjusting screw fully clockwise and check that the resistance changes from approx . 5 kS2 to 052 . 185 INSPECTION AND ADJUSTMENT - Variable Resisto r ECU O 00 000ooooory ❑ooooo000000~ W INSPECTION AND ADJUSTMENT - ISC Valv e ISC VALVE (DUTY-CONTROL ACV TYPE ) OBJECTIVE : To learn the procedure for inspecting the oxygen sensor . PREPARATIONS .  Ohmmeter ( also called "circuit tester" or "multi-tester")  12-V battery APPLICABLE ENGINE : 4A-FE (Sep ., 1989 ) INSPECTION OF ISC VALVE 1 . INSPECT ISC VALVE FOR OPEN CIRCUIT Using an ohmmeter, check for continuity between the terminals . Resistance: 2WD 30 - 33 S2 4WD 30 - 34 12 If there is no continuity, replace the ISC valve . 186 INSPECTION AND ADJUSTMENT - ISC Valv e 2 . INSPECT ISC VALVE FOR GROUNDING W Using an ohmmeter, check that there is no continuity between each terminal and body. If there is continuity, replace the ISC valve . 3 . INSPECT ISC VALVE OPERATION (a) Check that air does not flow from pipe E to pipe F . (b) Apply battery voltage across the terminals . (c) Check that air flows from pipe E to pipe F . If operation is not as specified, replace the ISC valve . 187 APPENDIX ENGINE CONTROL SYSTEM SPECIFICATION CHART ENGINE ENGINE G SIGNALS THROTTLE FUEL FEEDBACK ELECTRONIC SPARK KNOCK IDLE SPEE D CONTROL VALV E MODEL CONTROL 1 NE SIGNAL2 POSITION PATTERN IN T ON EC ADVANCE CONTROL AND/O R CONTROL'S AIR VALV E 1UZ-FE TCCS L-EF I (KS) G1, G2 (1 ) NE (12) Linear type 4 groups With o r Without With With Stepper moto r L-EFI j Independent j j (VG) (Sequential ) 3VZ-FE TCCS L-EFI G1, G2 (1) Linear type ype With or With With Stepper moto r ( ~VS) NE (24) (Sequential) Withou t 3VZ-E TCCS L-EF I VS G1, G2 (1 ) NE (24) Linear type Simultaneous With With With Thermo wax air (L ) valv e 5VZ-FE TCCS L-EFI G(1) Linear type Independent With With (DIS) With Rotary solenoi d (VG) NE (36-2) (Sequential) valv e 1 MZ-FE TCCS L-EFI G(1 ) Linear type Independent With or With (DIS) With Rotary solenoi d (VG) NE (36-2 ) (Sequential) Without valv e 2JZ-GE TCCS L-EF I (KSI G1, G211 1 NE (24) Linear type (Sequential) With With With Stepper moto r D-EFI j j With or j (PIM) Without j 3 groups Without j j j L-EFI G1,G2(1 ) NE 1241 Independent h W (VG) NE2 (36-2) (Sequential) it T 2JZ-GTE TCCS L-EF I (VG ) G1, G2 ( 1 ) NE (12) Linear type Independen t (Sequential) With With (DIS) With Stepper moto r 1G-FE EFI L-EF I 1 SVS) Without IDL, TL, PSW Simultaneous Without Without Without Thermowaxai r valve 3S-FE TCCS L-EFI G (4) Linear type or Simultaneous With or With Without Rotary solenoi d ( l,VSI NE (24 ) IDL, E, PSW Without valve D-EFI IDL, E PSW T Without t VSV & Therm o (PIM) , wax air valv e G (1) Linear type 2 groups With or With Rotary solenoi d NE (4) Without valve j NE (4) j Simultaneous With j j t Gil) j Independent j 1 NE (36-2) (Sequential ) 3S-GE TCCS L-EFI G1, G2 (1) Linear type Independent With or With Without VSV & Therm o ( (,VS) NE (24) (Sequential) Without wax air valve 1 ? With Rotary solenoid valve D-EFI j T j j j j j (PIM ) " For notes, see page 190 . 188 ENGINE ENGINE G SIGNALS THROTTLE FUEL FEEDBACK ELECTRONIC SPARK KNOCK IDLE SPEED CONTROL VALVE MODEL CONTROL . NESIGNAL2 POSITION INJECTION CORREC- ADVANCE CONTROL AND/OR SYSTEM" SENSOR*3 PATTERN TION*4 CONTROL`5 AIR VALV E 3S-GTE TCCS L-EFI G1, G2 (1) Linear type Independen t i S l) With With With Rotary solenoi d valv e ( (,VS) NE ( 24) equent a ( D-EFI ? j (PIM ) 5S-FE TCCS D-EFI G (4) Linear type Simultaneous With o r Wi h With Without Rotary solenoid l ( PIM) NE (24) or IDL, E, PSW t out v e va G(1) Linear type 2 groups r Wit h NE (4) G1, G2 ( 1 ) Independent With j NE (24) (Sequential ) G(1 ) j r NE (36-2 ) 4A-FE TCCS D-EFI G (4) IDL E PSW Simultaneous With or With Without ACV & Therm o (PIM) NE (24) , , Without wax air valve G1 , G2(1) Linear t pe o r D I Independent With (Lean j j Ni (24) E L LSW (Sequential) mix . sensor ) j Linear type j t Rotary solenoid valve G(1) 2 groups With or T With or NE (4) Without Withou t j* 6 G (1 ~ j With j With j NE (36 2) Independen t (Sequential ) 5A-FE TCCS D-EFI NE ( 4) Linear type Simultaneous With With With Rotary solenoi d l (PIM) va v e 7A-FE TCCS D-EFI G (1) Linear type 2 groups With With With Rotary solenoi d l v ( PIM) NE (4) va e G ( 1) Independent t NE (36-2) (Sequential ) 2E-E TCCS D-EFI NE (4) IDL E PSW Simultaneous With With Without Thermo wax ai r (PIM) , , valv e 4E-FE TCCS D-EF I (PIM) NE (4) IDL, E, PSW Simultaneous With With Without ACV & Therm o wax air valve j Li t j With or Rotary solenoi d near ype Without valve 5E-FE TCCS D-EFI G (1) Linear type 2 groups With With Without ACV & Therm o (PIM) NE ( 4) wax air valve j NE (4) j Simultaneous j t j Rotary solenoi d valv e C' (1) j 2 groups j With (DIS) Wit h NE (36-2 ) * For notes, see page 190 . 189 ENGINE ENGINE G SIGNALS THROTTLE FUEL FEEDBACK ELECTRONIC SPARK KNOCK IDLE SPEE D CONTROL VALV E MODEL CONTRO L ' , NESIGNAL+z POSITION  INJECTION CORREC- ADVANCE CONTROL AND/OR SYSTEM SENSOR 3 PATTERN TION'0 ' CONTROL S AIR VALV E 1 FZ-FE TCCS L-EF I ((,VS) G1, G2 (1 ) NE (24) Linear type Independen t (Sequential) With With With Stepper motor G (1 I With or T 1 1 NE (41 Without L-EFI i ? i ? ? 1 (VG) G1,G2 ( 1 ) ? NE (24) t With ? i ? NE2 (36-2 ) 1 RZ-E TCCS D-EFI NE (4) IDL E PSW Simultaneous With With With or Thermo wax ai r 2RZ-E (PIM) , , Without valv e 2RZ-FE TCCS L-EFI G(1) Linear type 2 groups With With With Rotary solenoi d 3RZ-FE (VG) NE (36-2) valv e 2TZ-FE TCCS L-EFI G1, G2 (1) Linear type Simultaneous With or With With Rotary solenoi d I~,VSI NE(24) Without valv e 2TZ-FZE TCCS L-EFI G(1 ) Linear type 2 groups With With With Rotary solenoi d (VG) NE (36-2) valv e 22R-E EFI L-EF I (1'VS) Without IDL, TL, PSW Simultaneous Without Without Without Bi-metal i l a r va v e TCCS ? NE (4) Linear type 1 With With With Bi-metal or Therm o wax air valve 4Y-E TCCS L-EFI NE (4) IDL, E, PSW Simultaneous With With Without VSV & Bi-meta l (1VS ) air valv e 1 2  3 a  5 .s The " ~ VS" means the type 1 air flow meter, while the "? VS" means the type 2 air flow meter . For further details, see page 20 . The numbers in the parentheses indicate the number of rotor teeth . Linear type throttle position sensor generally has IDL and VTA terminals . However, there are cases on some models that they do not use its circuit even if they have IDL terminal or they do not have IDL terminal itself . 02 sensor is used for the engines equipped with a feedback correction . The member of 02 sensor differs depending on the engine models and destinations . Fuel control switch or connector and fuel octane judgement are equipped on some models . Engine ECU made by Bosch is used . 190 0 TOYOTA 11 QUALITY SERVICE OVERSEAS SERVICE DIVISION TOYOTA MOTOR CORPORATION PRINTED IN JAPAN [c] 9109-N2-9710 NAME