DTC B1A02: Front Relay Control Module Battery (Buck Up) Power Supply

DTC detecting condition  :

When the backup power supply fuse is ON, battery voltage (backup) exceeded the range of 9 - 16 V for 40 seconds or more.

Trouble symptom  :

Answer-back buzzer does not sound

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. 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 B1A02 displayed? (Current code)

   Yes:  Go to  2.

   No:  Go to  5.

2. CHECK DTC  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the connectors (B68, B69) from Front relay control module.
   3. Connect the disconnected connectors.
   4. Turn the ignition switch to ON.
   5. Wait approx. 1 minute.
   6. 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 B1A02 displayed? (Current code)

   Yes:  Go to  3.

   No:  Go to  5.

3. CHECK FUSE  .
   1. Turn the ignition switch to OFF.
   2. Check the fuse. Ref. to WIRING SYSTEM>HEADLIGHT SYSTEM>WIRING DIAGRAM .

   Is the check result OK?

   Yes:  Go to  4.

   No:  Replace the defective fuse.

4. CHECK HARNESS (OPEN CIRCUIT)  .
   1. Disconnect the connector (B69) from Front relay control module.
   2. Using a tester, measure the voltage between Front relay control module connector and chassis ground.

      Connector & terminal 

      (B69) No. 10 (+) - Chassis ground (-):

   Is the voltage 8.5 - 16.5 V?

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

   No:  Repair the harness between Front relay control module and fuse.

5. CHECK CONNECTOR  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the connector (B69) from Front relay control module.

   Is there poor contact of Front relay control module connector?

   Yes:  Repair or replace the poor contact of connector.

   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.