2017 Subaru WRX BaseFACTORY OEM SERVICE PROCEDURE

Model With SRH

WARNING: This page is about a different car, the 2022 Subaru WRX. However, it is still accessible from the selected car via links, so may be relevant.

Wiring diagram: 

Headlight system Ref. to WIRING SYSTEM>HEADLIGHT SYSTEM>WIRING DIAGRAM

G14612340Courtesy of SUBARU OF AMERICA, INC.
  1. CHECK HEADLIGHT ILLUMINATION  .
    1. Turn the ignition switch to ON.
    2. Turn the lighting switch to the switch 1 (TAIL) position.
    3. Turn the lighting switch to the switch 2 (HEAD) position.
    4. Turn the dimmer & passing switch to the switch UP position.

    Do the parking light and headlight (low beam and high beam) come on?

    Yes  : The headlight system is normal.

    No  : Go to  2.

  2. CHECK DTC  .
    1. Turn the ignition switch to ON and wait for at least 10 seconds.
    2. Read the DTC of [Body Control] using the Subaru Select Monitor. Ref. to COMMON (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC)

    Is DTC displayed?

    Yes  : Perform the diagnosis for the displayed DTCs. Ref. to BODY CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC)>LIST

    No  : Go to  3.

  3. CHECK POWER SUPPLY  .

    Using the Subaru Select Monitor, display the following items in the [Data monitor] of [Body Control]. Ref. to COMMON (DIAGNOSTICS)>DATA MONITOR

    • [BATT voltage (control)]
    • [BATT voltage (BACKUP)]
    • [IGN voltage]

    Is the voltage 9 - 16 V?

    Yes  : Go to  4.

    No  : Check the body integrated unit and replace it if defective.

  4. CHECK CURRENT DATA  .
    1. Turn the ignition switch to ON.
    2. Using the Subaru Select Monitor, display the following items in the [Data monitor] of [Body Control]. Ref. to COMMON (DIAGNOSTICS)>DATA MONITOR
      • [Lighting II Switch Input]
      • [Dimmer Hi Switch Input]

    Does the display change between [OFF] ←→ [ON] when the lighting switch is moved to the switch 2 (HEAD) and switch UP (HI) positions?

    Yes  : Go to  5.

    No  : Check the combination switch or harness for open circuit.

  5. CHECK CURRENT DATA  .
    1. Turn the ignition switch to ON.
    2. Using the Subaru Select Monitor, display the following items in the [Data monitor] of [Body Control]. Ref. to COMMON (DIAGNOSTICS)>DATA MONITOR
      • [Lighting II Lamp Output]
      • [Lighting Hi Lamp Output]

    Does the display change to [ON] when turning the lighting switch to the switch 2 (HEAD) position and switch UP (HI) position?

    Yes  : Go to  6.

    No  : Replace the body integrated unit. Ref. to BODY CONTROL/COMMUNICATION SYSTEM>BODY INTEGRATED UNIT

  6. CHECK HARNESS  .
    1. Turn the ignition switch to OFF.
    2. Check the harness between the headlight connector and the chassis ground.

      Connector & terminal 

      Headlight RH 

      (B121) No. 4 - Chassis ground:

      Headlight LH 

      (B122) No. 4 - Chassis ground:

    Is the resistance less than 10 Ω?

    Yes  : Check the headlight assembly and replace it if defective.

    No  : Repair or replace the defective part.

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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.