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

Courtesy of SUBARU OF AMERICA, INC.

CAUTION:

Before performing diagnosis, refer to "CAUTION" in "General Description". Ref. to BODY CONTROL/COMMUNICATION SYSTEM>GENERAL DESCRIPTION>CAUTION .

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 malfunction)
  
  Yes: Go to 2 .
  
  No: Go to 5 .
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. Ref. to Front Relay Control Module (Diagnostics)>Diagnostic Trouble Code (DTC) .
  Is DTC B1A02 displayed? (Current malfunction)
  
  Yes: Go to 3 .
  
  No: Go to 5 .
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.
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.
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. Ref. 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.