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. CHECK STOP LIGHT & BRAKE SWITCH  .

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

   Is the check result for the stop light & brake switch 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 harness connector.
   3. Turn the ignition switch to ON.
   4. Measure the voltage between harness connector terminal and chassis ground.

      Connector & terminal

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

   Is the voltage 10 V or more?

   Yes: Go to  3.

   • Check the 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 harness connector terminal and chassis ground.

   Connector & terminal

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

   Is the voltage 10 V or more?

   Yes: Go to  4.

   • Check the 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 harness connector of ECM.
   3. Measure the resistance between ECM harness connector terminal and stop light & brake switch harness connector terminal.

      Connector & terminal

      (B65) No. 4 - (B134) No. 59:

      (B65) No. 2 - (B134) No. 48:

   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 harness connector.
   2. Turn the ignition switch to ON.
   3. Measure the voltage between ECM harness connector and chassis ground both when the brake pedal is depressed and when not depressed.

      Connector & terminal

      (B134) No. 59 (+) - Chassis ground (-):

      (B134) No. 48 (+) - Chassis ground (-):

   Does the voltage appear in (B134) No. 59 when the brake pedal is depressed? (0 V when the brake pedal is not depressed)

   Does the voltage appear in (B134) No. 48 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) (H6DO)>ENGINE CONTROL MODULE (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 .