DTC B278D: ID Code Box Judgment Circuit

DTC detecting condition: 

When the key is unregistered with the keyless access control module, the harness for the ID code BOX presence judgment is not connected, and also ID code BOX LIN response is present.

Trouble symptom: 

Initial registration for the access key is not possible.

Wiring diagram: 

Push button start system. Refer to WIRING SYSTEM>PUSH BUTTON START SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK DTC. 
   1. Turn the ignition switch to OFF.
   2. Perform the clear memory for «Keyless Access with Push Button Start» using the Subaru Select Monitor. Refer to KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM (DIAGNOSTICS)>CLEAR MEMORY .
   3. Turn the ignition switch to OFF → ON.
   4. Read DTCs of «Keyless Access with Push Button Start» using the Subaru Select Monitor. Refer to KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

      Is DTC B278D displayed? (Current malfunction)

      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.
2. CHECK HARNESS (OPEN CIRCUIT). 
   1. Disconnect the keyless access control module connector.
   2. Measure the resistance between keyless access control module connector and chassis ground.

      Connector & terminal 

      (B573) No. 18 - Chassis ground:

      Is the resistance less than 1 Ω?

      Yes:  Replace the keyless access control module. Refer to SECURITY AND LOCKS>KEYLESS ACCESS control module .

      No:  Repair or replace the open circuit of harness.