Check Headlight System

Trouble symptom:  Headlight does not illuminate, or headlight is weak.

1. CHECK HEADLIGHT ILLUMINATION  .
   1. Turn the ignition switch to ON.
   2. Turn the lighting switch to the switch 2 (HEAD) position and switch UP (HI) position.

   Does the 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.
   2. Turn the lighting switch to the switch 2 (HEAD) position and switch UP (HI) position.
   3. Read the DTC of [Front Relay Control Module] using the Subaru Select Monitor. Refer to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>Diagnostic Trouble Code (DTC) .

   Are any DTCs displayed?

   Yes  : Perform the diagnosis according to the displayed DTC. Refer to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>Diagnostic Trouble Code (DTC)>LIST .

   No  : Go to  3.

3. CHECK POWER SUPPLY  .

   Display the data of [BATT Voltage (Control)], [BATT Voltage (BACKUP)] and [IGN Voltage] using Subaru Select Monitor. Refer to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>DATA MONITOR .

   Is the voltage 9 - 16 V?

   Yes  : Go to  4.

   No  : Check the front relay control module and replace it if defective.

   • Inspection: Refer to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>Basic Diagnostic Procedure .
   • Replacement: Refer to BODY CONTROL/COMMUNICATION SYSTEM>FRONT RELAY CONTROL MODULE .
4. PERFORM ACTIVE TEST  .

   Using the Subaru Select Monitor, check the following items in the [Active Test] of [Front Relay Control Module]. Refer to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>ACTIVE TEST .

   NOTE: Check the items where illumination did not occur in step 1).
   • [Lighting Low RH Output]
   • [Lighting Low LH Output]
   • [Lighting High RH Output]
   • [Lighting High LH Output]

   Does the light illuminate?

   Yes  : Go to  9.

   No  : Go to  5.

5. CHECK HEADLIGHT POWER SUPPLY CIRCUIT  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the front relay control module connector.
   3. Measure the voltage between front relay control module connector and chassis ground.

      Connector & terminal 

      Headlight RH

      (B68) No. 1 (+) - Chassis ground (-):

      Headlight LH

      (B69) No. 6 (+) - Chassis ground (-):

   Is the voltage 9 - 16 V?

   Yes  : Go to  6.

   No  : Check the harness of the fuse, connector and power supply circuit. If there are no problems, replace the front relay control module. Refer to BODY CONTROL/COMMUNICATION SYSTEM>FRONT RELAY CONTROL MODULE .

6. CHECK HARNESS  .
   1. Disconnect the connector of the light which did not illuminate.
   2. Check the harness between the front relay control module and the headlight.

      Connector & terminal 

      Headlight RH (low beam)

      (B68) No. 2 - (B121) No. 10: Headlight RH (high beam)

      (B69) No. 2 - (B121) No. 6: Headlight LH (low beam)

      (B69) No. 8 - (B122) No. 10: Headlight LH (high beam)

      (B69) No. 7 - (B122) No. 6:

   Is harness normal?

   Yes  : Go to  7.

   No  : Repair or replace the harness.

7. CHECK HEADLIGHT  .

   Apply battery voltage between headlight unit connector terminals.

   CAUTION: Make sure that the high beam illuminates because the high beam shares the same lighting body with the low beam and they are alternatively lit by switching.

   Connector & terminal 

   If the low beam does not illuminate 

   Headlight RH

   (B121) No. 10 (+) - (B121) No. 14 (-):

   Headlight LH

   (B122) No. 10 (+) - (B122) No. 14 (-):

   If the high beam does not illuminate 

   Headlight RH

   (B121) No. 10 and (B121) No. 6 (+) - (B121) No. 14 (-):

   Headlight LH

   (B122) No. 10 and (B122) No. 6 (+) - (B122) No. 14 (-):

   Does the headlight (low beam and high beam) come on at normal brightness?

   Yes  : Go to  8.

   No  : Replace the headlight assembly. Refer to LIGHTING SYSTEM>Headlight Assembly .

8. CHECK HARNESS  .

   Check the harness between the headlight connector and the chassis ground.

   Connector & terminal 

   Headlight RH 

   (B121) No. 14 - Chassis ground:

   Headlight LH 

   (B122) No. 14 - Chassis ground:

   Is harness normal?

   Yes  : Check the front relay control module and replace it if defective.

   • Inspection: Refer to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>Basic Diagnostic Procedure .
   • Replacement: Refer to BODY CONTROL/COMMUNICATION SYSTEM>FRONT RELAY CONTROL MODULE .

   No  : Repair or replace the harness.

9. CHECK CURRENT DATA  .
   1. Turn the ignition switch to ON.
   2. Display the data of [Lighting II Switch Input] and [Dimmer Hi Switch Input] using Subaru Select Monitor. Refer to BODY CONTROL (DIAGNOSTICS)>DATA MONITOR .

   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  10.

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

10. CHECK CURRENT DATA  .
    1. Turn the ignition switch to ON.
    2. Display the data of [Lighting Low Request] and [Lighting High Request] using Subaru Select Monitor. Refer to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>DATA MONITOR .

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

    Yes  : Replace the front relay control module. Refer to BODY CONTROL/COMMUNICATION SYSTEM>FRONT RELAY CONTROL MODULE .

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