DTC B1502: Warning Box Communication Malfunction

DTC detecting condition  :

Communication error between the combination meter and warning box.

Trouble symptom  :

Improper operation of the warning light in the warning box

Failure detection pattern  :

• Detection by a single system (Primary Failure)

Wiring diagram  :

Combination meter system Ref. to WIRING SYSTEM>COMBINATION METER SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

1. BASIC INSPECTION  .

   Before performing the diagnosis, perform basic inspection. Ref. to COMBINATION METER (DIAGNOSTICS)>GENERAL DESCRIPTION>INSPECTION .

   NOTE:

   • Check the battery and its installation condition.
   • Check the related fuse.
   • Visually check that the related connectors are properly connected.

     Also, check the related ground terminal for looseness and corrosion.

   Is the check result OK?

   Yes  : GO TO  2.

   No  : Repair the defective part.

2. CHECK POWER SUPPLY CIRCUIT  .

   Turn the ignition switch to ON, and make sure that the combination meter operates properly.

   Is the check result OK?

   Yes  : GO TO  3.

   No  : Check the combination meter power supply circuit.

   After the repair, GO TO  10.

3. CHECK WARNING BOX  .

   Turn the ignition switch to ON and check that the waring light in the warning box starts blinking.

   Is the check result OK?

   Yes  : GO TO  6.

   No  : GO TO  4.

4. CHECK WARNING BOX POWER SUPPLY VOLTAGE  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the warning box connector.
   3. Turn the ignition switch to ON.
   4. Measure the voltage between the warning box connector and chassis ground.

      Connector & terminal 

      (Rf23) No. 4 (+) - Chassis ground (-)  :

   Is the voltage 10 V or more?

   Yes  : Replace the warning box. Ref. to INSTRUMENTATION/DRIVER INFO>WARNING BOX .

   After replacement, GO TO  10.

   No  : GO TO  5.

5. CHECK WARNING BOX POWER SUPPLY VOLTAGE  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the Rf11 connector.
   3. Turn the ignition switch to ON.
   4. Measure the voltage between the Rf11 connector and chassis ground.

      Connector & terminal 

      (Rf11) No. 3 (+) - Chassis ground (-)  :

   Is the voltage 10 V or more?

   Yes  : Replace the map light. Ref. to LIGHTING SYSTEM>SPOT MAP LIGHT .

   After replacement, GO TO  10.

   No  : Repair the open circuit of harness or replace harness.

   After the repair, GO TO  10.

6. CHECK DTC  .

   Read the DTC of [Combination Meter] using the Subaru Select Monitor. Ref. to COMBINATION METER (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Is DTC B1502 displayed? (Current code)

   Yes  : GO TO  7.

   No  : GO TO  9.

7. CHECK COMMUNICATION CIRCUIT (HARNESS) (OPEN CIRCUIT)  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the connector from the combination meter.
   3. Disconnect the connector from the warning box.
   4. Using a tester, measure the resistance between the combination meter connector and warning box connector.

      Connector & terminal 

      (i97) No. 12 - (Rf23) No. 2  :

   Is the resistance less than 10 Ω?

   Yes  : Replace the warning box. Ref. to INSTRUMENTATION/DRIVER INFO>WARNING BOX .

   After replacement, GO TO  10.

   No  : GO TO  8.

8. CHECK COMMUNICATION CIRCUIT (HARNESS) (OPEN CIRCUIT)  .

   Using a tester, measure the resistance between the Rf3 connector and warning box connector.

   Connector & terminal 

   (Rf3) No. 2 - (Rf23) No. 2  :

   Is the resistance less than 10 Ω?

   Yes  : Repair the open circuit of harness between combination meter connector and warning box connector.

   After the repair, GO TO  10.

   No  : Replace the map light. Ref. to LIGHTING SYSTEM>SPOT MAP LIGHT .

   After replacement, GO TO  10.

9. CHECK CONNECTOR  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the connector from the combination meter.
   3. Disconnect the connector from the warning box.
   4. Check the connector.

   Is there any fault in the connector?

   Yes  : Repair or replace the connector.

   After the repair, GO TO  10.

   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.

   After the repair, GO TO  10.

10. CHECK REPAIR  .
    1. Perform the inspection mode corresponding to DTC. Ref. to COMBINATION METER (DIAGNOSTICS)>INSPECTION MODE>OPERATION .
    2. Confirm that DTC or cancel code is not stored and the malfunction is eliminated.

    Is the check result OK?

    Yes  : Finish the diagnosis.

    No  : Perform the diagnosis according to the basic diagnostic procedure. Ref. to COMBINATION METER (DIAGNOSTICS)>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE .