DTC B1012: Battery Backup Power Supply

DTC detecting condition: 

Voltage failure caused by poor contact of battery power supply backup circuits

Trouble symptom: 

Illuminations for the keyless entry, map light, trunk light, room light, and ignition switch do not turn on.

Wiring diagram: 

Interior light system Ref. to WIRING SYSTEM>INTERIOR LIGHT SYSTEM>WIRING DIAGRAM

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK DTC  .
   1. Turn the ignition switch to ON.
   2. Read the DTC of [Body Control] using the Subaru Select Monitor. Ref. to BODY CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) 

   Is DTC B1012 displayed? (Current code)

   Yes  : Go to  2.

   No  : Go to  5.

2. CHECK DTC  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the connector from body integrated unit.
   3. Connect the disconnected connectors.
   4. Wait approx. 2 minutes.
   5. Turn the ignition switch to ON.
   6. Read the DTC of [Body Control] using the Subaru Select Monitor. Ref. to BODY CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) 

   Is DTC B1012 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>INTERIOR LIGHT SYSTEM>WIRING DIAGRAM

   Is the check result OK?

   Yes  : Go to  4.

   No  : Replace the defective fuse.

4. CHECK HARNESS  .
   1. Disconnect the connector from body integrated unit.
   2. Measure the voltage between body integrated unit and chassis ground using tester.

      Connector & terminal 

      (B73) No. 7 (+) - Chassis ground (-):

   Is the voltage 8.5 - 16.5 V?

   Yes  : Replace the body integrated unit. Ref. to BODY CONTROL/COMMUNICATION SYSTEM>BODY INTEGRATED UNIT

   No  : Repair the harness between body integrated unit and fuse.

5. CHECK CONNECTOR  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the connector from body integrated unit.

   Is there poor contact of 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.