Diagnostic Procedure with Cancel Code: 12

Detected when the brake pedal is depressed, or the error related to the stop light & brake switch occurred.

Trouble symptom: 

• Cruise control cannot be set.
• Cruise control cannot be released.

Wiring diagram: 

Cruise control system Ref. to WIRING SYSTEM>CRUISE CONTROL SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

1. PERFORM UNIT INSPECTION OF STOP LIGHT & BRAKE SWITCH  .

   Check the stop light & brake switch. Ref. to CRUISE CONTROL SYSTEM>STOP LIGHT & BRAKE SWITCH .

   Are the check results for the stop light & brake switch unit, and installation position OK?

   Yes  : Go to  2 .

   No  : Replace the stop light & brake switch. Or adjust the installation position.

2. CHECK STOP LIGHT & BRAKE SWITCH CIRCUIT  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the stop light & brake switch connector.
   3. Turn the ignition switch to ON.
   4. Measure the voltage between the stop light & brake switch connector and chassis ground.

   Connector & terminal

   (B65) No. 1 (+) - Chassis ground (-):

   Is the voltage 10 V or more?

   Yes  : Go to  3 .

   No  :

   • Check fuse No. 37 (fuse & relay box).
   • Check for open or short circuit in harness between the stop light & brake switch and the fuse & relay box.
3. CHECK STOP LIGHT & BRAKE SWITCH CIRCUIT  .

   Measure the voltage between the stop light & brake switch connector and chassis ground.

   Connector & terminal

   (B65) No. 5 (+) - Chassis ground (-):

   Is the voltage 10 V or more?

   Yes  : Go to  4 .

   No  :

   • Check fuse No. 19 (fuse & relay box).
   • Check for open or short circuit in harness between the stop light & brake switch and the fuse & relay box.
4. CHECK STOP LIGHT & BRAKE SWITCH CIRCUIT  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the ECM connector.
   3. Measure the resistance between the ECM connector and stop light & brake switch connector.

   Connector & terminal

   (B65) No. 4 - (B134) No. 36:

   (B65) No. 2 - (B134) No. 38:

   Is the resistance less than 10 Ω?

   Yes  : Go to  5 .

   No  : Repair the harness.

5. CHECK STOP LIGHT & BRAKE SWITCH CIRCUIT  .
   1. Connect the stop light & brake switch connector.
   2. Turn the ignition switch to ON.
   3. Measure the voltage between ECM connector and chassis ground both when the brake pedal is depressed and when not depressed.

   Connector & terminal

   (B134) No. 36 (+) - Chassis ground (-):

   (B134) No. 38 (+) - Chassis ground (-):

   Does the voltage appear in (B134) No. 36 when the brake pedal is depressed? (0 V when the brake pedal is not depressed)

   Does the voltage appear in (B134) No. 38 when the brake pedal is not depressed? (0 V when the brake pedal is depressed)

   Yes  : Replace the ECM. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO)>ENGINE CONTROL MODULE (ECM) .

   No  : Replace the stop light & brake switch. Ref. to CRUISE CONTROL SYSTEM>STOP LIGHT & BRAKE SWITCH .