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. Ref. to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

      Are any DTCs displayed?

      Yes  : Perform the diagnosis according to the displayed DTC. Ref. 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. Ref. 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: Ref. to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>BASIC DIAGNOSTIC PROCEDURE .
   • Replacement: Ref. 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]. Ref. 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 and 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. Ref. 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 and 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.
   • When applying battery voltage, do not mix up the positive (+) side and the negative (-) side. Incorrect polarity connection may cause internal LED damage.

   Connector and terminal 

   1. If the low beam does not illuminate 

      Headlight RH 

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

      Headlight LH 

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

   2. 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. Ref. to LIGHTING SYSTEM>HEADLIGHT ASSEMBLY .

8. CHECK HARNESS  .

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

   Connector and 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: Ref. to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>BASIC DIAGNOSTIC PROCEDURE .
   • Replacement: Ref. 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. Ref. 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. Ref. 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. Ref. to BODY CONTROL/COMMUNICATION SYSTEM>FRONT RELAY CONTROL MODULE .

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