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: 

-

Wiring diagram: 

Headlight system Refer to WIRING SYSTEM>Headlight System>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK DTC  .

   Read the DTC of [Front Relay Control Module] using the Subaru Select Monitor. Refer to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Is DTC B1A02 displayed? (Current malfunction)

   Yes  : Go to  2.

   No  : Go to  5.

2. CHECK DTC  .
   1. Turn the ignition switch to OFF.
   2. Disconnect Front relay control module connectors (B68, B69) and reconnect them.
   3. Turn the ignition switch to ON.
   4. Wait approx. 1 minute.
   5. Read the DTC of [Front Relay Control Module] using the Subaru Select Monitor. Refer to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Is DTC B1A02 displayed? (Current malfunction)

   Yes  : Go to  3.

   No  : Go to  5.

3. CHECK FUSE  .
   1. Turn the ignition switch to OFF.
   2. Check the fuse.

   Is the check result OK?

   Yes  : Go to  4.

   No  : Replace the defective fuse.

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

      Connector & terminal 

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

   Is the voltage 8.5 - 16.5 V?

   Yes  : Go to  5.

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

5. CHECK CONNECTOR  .
   1. Turn the ignition switch to OFF.
   2. Disconnect Front relay control module connectors (B68, B69).

   Is there poor contact of connector?

   Yes  : When moved from step 1 or step 2: Repair or replace the poor contact of connector.

   When moved from step 4: Repair or replace the connector, and check DTC. When DTC B1A02 is displayed, replace the Front relay control module. Refer to BODY CONTROL/COMMUNICATION SYSTEM>FRONT RELAY CONTROL MODULE .

   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.