DTC B1A0C: Front Relay Control Module Can Register Stuck

WARNING: This page is about a different car, the 2022 Subaru WRX. However, it is still accessible from the selected car via links, so may be relevant.

DTC detecting condition:

The written value and read value differ, when "AAH" and "55H" are written to the CAN controller ID, DLC and message box registers during the transition of CAN communication mode (unit initialization mode or bus sleep mode) to normal communication mode, and then are read out.

Trouble symptom:

The headlight High does not illuminate.

CAUTION:

Before performing diagnosis, refer to "CAUTION" in "General Description". Ref. to FRONT RELAY CONTROL MODULE (DIAGNOSTICS)>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 B1A0C displayed? (Current code)

Yes : Go to 2.

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.
CHECK CONNECTOR .
1. Turn the ignition switch to OFF.
2. Disconnect the body integrated unit connector.
3. Connect the disconnected connectors.
4. Turn the ignition switch to ON.
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 B1A0C displayed? (Current code)

Yes : Replace 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.