DTC B2904: Led Headlight Circuit RH

DTC detecting condition: 

Failure status of the RH headlight malfunction signal is detected for two seconds continuously.

Trouble symptom: 

LED headlight malfunction, LED headlight indicator illuminates.

Wiring diagram: 

• Headlight beam leveler system Ref. to WIRING SYSTEM>HEADLIGHT BEAM LEVELER SYSTEM>WIRING DIAGRAM
• Headlight system Ref. to WIRING SYSTEM>HEADLIGHT SYSTEM>WIRING DIAGRAM

• Without SRH

  Courtesy of SUBARU OF AMERICA, INC.

• With SRH

  Courtesy of SUBARU OF AMERICA, INC.

1. CHECK DTC  .
   1. Turn the ignition switch OFF → ON.
   2. Using the Subaru Select Monitor, perform the clear memory of [Headlight/Foglight]. Ref. to COMMON (DIAGNOSTICS)>CLEAR MEMORY
   3. Turn the ignition switch to OFF → ON.
   4. Turn the lighting switch to 2 (HEAD).
   5. Read the DTC of [Headlight/Foglight] using the Subaru Select Monitor. Ref. to HEADLIGHT/FOGLIGHT (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) 

   Is DTC B2904 displayed? (Current code)

   Yes  : Go to  2.

   No  : Even if DTC is displayed, the circuit has returned to a normal condition at this time. Reproduce the failure, and then perform the diagnosis again.

   NOTE:

   In this case, temporary poor contact of connector, temporary open or short circuit of harness may be the cause. 

2. CHECK DATA MONITOR  .

   Using the Subaru Select Monitor, check the following items in the [Data Monitor] of [Headlight/Foglight]. Ref. to HEADLIGHT/FOGLIGHT (DIAGNOSTICS)>DATA MONITOR 

   • LED HEADLAMP (RH) error Signal

   Does the data display [OFF]?

   Yes  : Replace the auto headlight beam leveler control module. Ref. to LIGHTING SYSTEM>AUTO HEADLIGHT BEAM LEVELER CONTROL MODULE

   No  : Go to  3.

3. CHECK THE HEADLIGHT SYSTEM POWER SUPPLY CIRCUIT  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the connector from the headlight assembly RH.
   3. Disconnect the connector from the headlight assembly LH.
   4. Turn the ignition switch to ON.
   5. Turn the lighting switch to 2 (HEAD).
   6. Using a tester, measure the voltage between headlight assembly RH connector and chassis ground.

      Connector & terminal 

      (B121) No. 1 (+) - Chassis ground (-):

   Is the voltage 10 - 13 V?

   Yes  : Go to  4.

   No  : Repair the headlight system.

4. CHECK HARNESS (OPEN CIRCUIT)  .
   1. Turn the ignition switch to OFF.
   2. Using a tester, measure the resistance between headlight assembly RH connector and chassis ground.

      Connector & terminal 

      Without SRH 

      (B121) No. 2 - Chassis ground:

      With SRH 

      (B121) No. 6 - Chassis ground:

   Is the resistance less than 10 Ω?

   Yes  : Go to  5.

   No  : Repair or replace the open circuit of harness.

5. CHECK HEADLIGHT SYSTEM  .
   1. Connect the headlight assembly RH connector.
   2. Turn the ignition switch to ON.
   3. Turn the lighting switch to 2 (HEAD).

   Does the headlight come on at normal brightness?

   Yes  : Go to  6.

   No  : Replace the headlight. Ref. to LIGHTING SYSTEM>HEADLIGHT ASSEMBLY

6. CHECK HARNESS (OPEN CIRCUIT)  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the connector from the auto headlight beam leveler control module.
   3. Using a tester, measure the resistance between auto headlight beam leveler control module connector and headlight assembly RH connector.

      Connector & terminal 

      Without SRH 

      (B78) No. 12 - (B121) No. 4:

      With SRH 

      (B78) No. 12 - (B121) No. 5:

   Is the resistance less than 10 Ω?

   Yes  : Go to  7.

   No  : Repair or replace the open circuit of harness.

7. CHECK HARNESS (OPEN CIRCUIT)  .

   Using a tester, measure the resistance between the auto headlight beam leveler control module connector and chassis ground.

   Connector & terminal 

   (B78) No. 2 - Chassis ground:

   Is the resistance less than 10 Ω?

   Yes  : Replace the auto headlight beam leveler control module. Ref. to LIGHTING SYSTEM>AUTO HEADLIGHT BEAM LEVELER CONTROL MODULE

   No  : Repair or replace the open circuit of harness.