Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Basic Diagnostic Procedure: Procedure: Engine
- CHECK ENGINE START FAILURE
.
- Ask the customer when and how the trouble occurred using the interview check list. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>Check List for Interview>CHECK .
- Start the engine.
Does the engine start?
Yes: Go to 2.
No: Inspection using "Diagnostics for Engine Starting Failure". Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>DIAGNOSTICS FOR ENGINE STARTING FAILURE .
- CHECK ILLUMINATION OF MALFUNCTION INDICATOR LIGHT
.
Does the malfunction indicator light illuminate?
Yes: Go to 3.
No: Inspection using "General Diagnostic Table". Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>GENERAL DIAGNOSTIC TABLE .
- CHECK COMMUNICATION STATUS
.
- Turn the ignition switch to OFF.
- Connect the Subaru Select Monitor or general scan tool to the data link connector.
- Turn the ignition switch to ON, and run the Subaru Select Monitor or general scan tool.NOTE:
- SUBARU SELECT MONITOR
For detailed procedures, refer to "Subaru Select Monitor". Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>SUBARU SELECT MONITOR .
- General scan tool
For detailed operation procedures, refer to the general scan tool operation manual.
- SUBARU SELECT MONITOR
Does Subaru Select Monitor communicate with vehicle normally?
Yes: Go to 4.
No: Inspection using "Basic Diagnostic Procedure" of LAN system. Ref. to LAN SYSTEM (DIAGNOSTICS)>BASIC DIAGNOSTIC PROCEDURE .
- CHECK DTC
.
Read DTC using Subaru Select Monitor or general scan tool.
NOTE:- Subaru Select Monitor
Refer to "Read Diagnostic Trouble Code (DTC)" for detailed operation procedure. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>READ DIAGNOSTIC TROUBLE CODE (DTC) .
- General scan tool
For detailed operation procedures, refer to the general scan tool operation manual.
Is DTC displayed on Subaru Select Monitor or general scan tool?
Yes: Record DTC, time stamp, and freeze frame data, then repair the trouble cause. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>LIST OF DIAGNOSTIC TROUBLE CODE (DTC) . After repair, go to the next step. Go to 5.
NOTE:- For the time stamp, refer to LAN service information. Ref. to LAN SYSTEM (DIAGNOSTICS)>General Description>CAUTION>TIME STAMP .
- Depending on DTCs, time stamp may not be stored.
No: Repair the related parts.
NOTE: If DTC is not shown on display although the malfunction indicator light illuminates, perform the diagnosis of malfunction indicator light circuit or combination meter. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>MALFUNCTION INDICATOR LIGHT . - Subaru Select Monitor
- PERFORM DIAGNOSIS
.
- Clear the memory. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>CLEAR MEMORY MODE .
- Perform the Inspection Mode or Drive Cycle. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>INSPECTION MODE . Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>DRIVE CYCLE .
Is DTC displayed on Subaru Select Monitor or general scan tool?
Yes: Inspect using "Diagnostic Procedure with Diagnostic Trouble Code (DTC)".
Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC) .
No: Finish the diagnosis.
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.