Subaru Forester Full Workshop Manual. Wiring Diagram

These pages contain a detailed guide to diagnosing and repairing DTC (Diagnostic Trouble Codes) errors for the Subaru Forester.

(SF, 1997–2002), (SG, 2002–2008), (SH, 2008–2013), (SJ, 2012–2018), (SK, 2018–2023), (SK Facelift & Wilderness, 2023–2025).

Engine: EJ20, EJ25, EE20, FB20, FB25, FA20DIT, CB18, e-BOXER.

📌 Main sections:

🔧 Decoding error codes - a detailed description of each DTC code.

🛠 Causes of malfunctions - possible sources of the problem.

📍 Diagnostic methods - instructions for checking sensors, connectors and circuits.

⚡ Repair recommendations - replacing faulty components, eliminating short circuits and open circuits.

🔍 Using OBD2 scanners - methods for reading and resetting error codes.

This section will help mechanics and owners quickly identify and fix malfunctions related to the engine, transmission, electronics and other Subaru Forester systems. 🚗🔧📘

• Subaru All Models>>
• Forester SF Wiring Diagram>>
• Forester SG, 2002–2008 Workshop Manual>>
• Forester SH, 2008–2013 Workshop Manual>>

1. Engine (EJ20, EJ25)

🔧 Oil consumption – EJ25 engines (2.5 l) tend to burn more oil due to worn piston rings and stuck oil scraper rings.

🛠 Problematic cylinder head gaskets – often burn out on EJ25, causing overheating and antifreeze leaks.

⚡ Engine knocking (piston rumble) – typical for boxer engines, especially when cold.

Solution:

✔️ Regular oil changes (5W-40 or 10W-40).

✔️ Check antifreeze levels and replace cylinder head gaskets with multilayer metallized (MLS).

2. Automatic transmission (4EAT)

⚙️ Jerks when shifting – wear of the valve body and solenoids.

🚨 Delays in gear engagement are a sign of contaminated oil or wear of internal components.

Solution:

✔️ Change automatic transmission oil every 40–50 thousand km.

✔️ Clean or replace solenoids at the first sign of problems.

3. All-wheel drive (AWD)

🛠 Viscous coupling failure (on manual transmission) – with abrupt starts or frequent slippage, the viscous coupling overheats and loses efficiency.

🔧 Jerking when turning (automatic transmission) – problems with rear axle locking due to a faulty AWD clutch solenoid.

Solution:

✔️ Use only the same size tires on all wheels.

✔️ Check and replace oil in the rear differential.

4. Body and corrosion

❄️ Rust on thresholds, arches and underbody – weak factory anti-corrosion treatment.

🚪 Problems with door locks – in winter, locks freeze or become sour.

Solution:

✔️ Additional anti-corrosion treatment.

✔️ Lubrication of locks and seals with silicone grease.

5. Electrics and sensors

⚠️ Faulty mass air flow sensor (MAF) – causes triple misfires and loss of power.

🔋 Weak generator – may not produce the required voltage in cold weather.

💡 Burnt contacts in the fuse box – leads to problems with lighting and the heater fan.

Solution:

✔️ Cleaning the MAF sensor at each maintenance.

✔️ Checking the generator voltage and installing a more powerful one if necessary.