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, luggage light, trunk light, room light, and ignition switch do not turn on.

Wiring diagram: 

Immobilizer system Ref. to WIRING SYSTEM (IMPREZA MODEL)>IMMOBILIZER SYSTEM>WIRING DIAGRAM . Ref. to WIRING SYSTEM (CROSSTREK MODEL (EXCEPT FOR HEV))>IMMOBILIZER SYSTEM>WIRING DIAGRAM . Ref. to WIRING SYSTEM (CROSSTREK MODEL (HEV)) IMMOBILIZER 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 malfunction)

      Yes  : Go to  2.

      No  : Go to  5.

2. CHECK DTC  .
   1. Turn the ignition switch to OFF.
   2. Disconnect and then connect the body integrated unit connector.
   3. Wait approx. 2 minutes.
   4. Turn the ignition switch to ON.
   5. 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 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  .
   1. Disconnect the body integrated unit connector.
   2. Using the tester, measure the voltage between terminals.

      Connector & terminal 

      (B281) No. 7 (+) - Chassis ground (-):

      Is the voltage 8.5 - 16.5 V?

      Yes  : Replace the body integrated unit. Ref. to SECURITY AND LOCKS>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 body integrated unit connector.

      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.