2018 Subaru WRX STIFACTORY OEM SERVICE PROCEDURE

Basic Diagnostic Procedure: Procedure: Engine

  1. CHECK ENGINE START FAILURE  .
    1. Ask the customer when and how the trouble occurred using the interview check list. Ref. to ENGINE (DIAGNOSTICS) (STI)>Check List for Interview>CHECK .
    2. Start the engine.

    Does the engine start?

    Yes: Go to  2.

    No: Inspection using "Diagnostics for Engine Starting Failure" Ref. to ENGINE (DIAGNOSTICS) (STI)>Diagnostics for Engine Starting Failure .

  2. 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) (STI)>General Diagnostic Table .

  3. CHECK COMMUNICATION STATUS  .
    1. Turn the ignition switch to OFF.
    2. Connect the Subaru Select Monitor or general scan tool to the data link connector.
    3. Turn the ignition switch to ON, and run the Subaru Select Monitor or general scan tool.
      NOTE:
      • Subaru Select Monitor

        For detailed operation procedures, refer to the "Subaru Select Monitor". Ref. to ENGINE (DIAGNOSTICS) (STI)>Subaru Select Monitor .

      • General scan tool

        For detailed operation procedures, refer to the general scan tool operation manual.

    Does Subaru Select Monitor or general scan tool communicate with vehicle normally?

    Yes: Go to  4.

    No: Inspection using "Diagnostic Procedure for Subaru Select Monitor Communication". Ref. to ENGINE (DIAGNOSTICS) (STI)>Diagnostic Procedure for Subaru Select Monitor Communication .

  4. CHECK DTC  .

    Read DTC using Subaru Select Monitor or general scan tool.

    NOTE:

    Is DTC displayed on Subaru Select Monitor or general scan tool?

    Yes: Record DTC and freeze frame data, then repair the trouble cause. Ref. to ENGINE (DIAGNOSTICS) (STI)>List of Diagnostic Trouble Code (DTC) . after repair, go to the next step. GO to  5.

    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) (STI)>Malfunction Indicator Light .
  5. PERFORM DIAGNOSIS  .
    1. Perform the Clear Memory Mode. Ref. to ENGINE (DIAGNOSTICS) (STI)>Clear Memory Mode .
    2. Perform the Inspection Mode or Drive Cycle. Ref. to ENGINE (DIAGNOSTICS) (STI)>Inspection Mode . Ref. to ENGINE (DIAGNOSTICS) (STI)>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 WRX STI (2.5L) .

    No: Finish the diagnosis.

Factory Service Tools

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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.

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