DTC B278D: Id Code Box Judgment Circuit

DTC detecting condition: 

When there is no connection of harness for ID code BOX presence judgment and ID code BOX LIN response is present while keyless access control module has no key registration.

Trouble symptom: 

Initial registration for the access key is not possible.

Wiring diagram: 

Keyless access with push button start system Ref. to WIRING SYSTEM>KEYLESS ACCESS WITH PUSH BUTTON START SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK DTC  .
   1. Turn the ignition switch to ON.
   2. Using the Subaru Select Monitor, perform the clear memory of [Keyless Access with Push Button Start(Collation)]. Ref. to COMMON (DIAG)>CLEAR MEMORY .
   3. Turn the ignition switch to OFF → ON.
   4. Read the DTC of [Keyless Access with Push Button Start(Collation)] using the Subaru Select Monitor. Ref. 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  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the keyless access control module connector.
   3. Measure the resistance between keyless access control module connector and chassis ground.

      Connector and terminal 

      (i91) No. 18 - Chassis ground:

   Is the resistance less than 1 Ω?

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

   No  : Repair or replace the open circuit of harness.