DTC B1A04: Head Lamp Lo LH Circuit Current High

DTC detecting condition: 

When over-current is detected while the headlight Low is output.

Trouble symptom: 

Left side of the headlight Low does not illuminate.

Wiring diagram: 

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

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK DTC  .
   1. Turn the ignition switch to ON.
   2. Turn the lighting II SW to ON.
   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) .

      Is DTC B1A04 displayed? (Current malfunction)

      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 FRONT COMBINATION LIGHT LH  .
   1. Using the Subaru Select Monitor, check the following items of [Active Test] of [Front Relay Control Module]. Ref. to Active Test .
      • Lighting Low LH Output
   2. Check that the left side of headlight Low illuminates.

      Is the check result OK?

      Yes:  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. 

      No:  Go to  3 .

3. CHECK CONNECTOR  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the Front relay control module connector.

      Is there poor contact of connector?

      Yes:  Repair or replace the poor contact of connector.

      No:  Go to  4 .

4. CHECK HARNESS (GROUND SHORT CIRCUIT)  .
   1. Disconnect the front combination light LH connector.
   2. Using a tester, measure the resistance between Front relay control module connector and chassis ground.

      Connector & terminal 

      (B69) No. 8 - Chassis ground:

      Is the resistance 1 MΩ or more?

      Yes:  Go to  5 .

      No:  Repair or replace the short circuit of the harness.

5. CHECK FRONT COMBINATION LIGHT LH  .
   1. Apply a voltage equivalent to the battery voltage between the front combination light LH connector terminals.

      Connector & terminal 

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

   2. Check that the left side of headlight Low illuminates.

      Is the check result OK?

      Yes:  Replace Front relay control module. Ref. to BODY CONTROL/COMMUNICATION SYSTEM>FRONT RELAY CONTROL MODULE .

      No:  Replace the front combination light LH. Ref. to LIGHTING SYSTEM>HEADLIGHT ASSEMBLY .