Diagnostic Procedure With ECU Cancel Code: 12

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

Trouble symptom:

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

Wiring diagram:

Stop light system Ref. to WIRING SYSTEM>STOP LIGHT SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

CAUTION: Before performing diagnosis, refer to "CAUTION" in "General Description". Ref. to EYESIGHT (DIAGNOSTICS)>General Description>CAUTION .

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

Is the check result for the stop light and brake switch installation position OK?

Yes : Go to 2 .

No : Replace the stop light and brake switch. Or adjust the installation position.
CHECK STOP LIGHT AND BRAKE SWITCH CIRCUIT .
1. Turn the ignition switch to OFF.
2. Disconnect the ground terminal from battery sensor. Ref. to GROUND TERMINAL REMOVAL OR INSTALLATION .
3. Disconnect the stop light and brake switch connector.
4. Using a tester, measure the resistance between the connector terminal and chassis ground.
  Connector and terminal
  
  (B65) No. 3 - Chassis ground:
  
  Is the resistance less than 10 Ω?
  
  Yes : Go to 3 .
  
  No : Check the ground system circuit, and if any fault is found, repair the defective parts or replace the harness.
CHECK STOP LIGHT AND BRAKE SWITCH CIRCUIT .
1. Connect the ground terminal to battery sensor. Ref. to GROUND TERMINAL REMOVAL OR INSTALLATION .
2. Turn the ignition switch to ON.
3. Measure the voltage between connector terminal and chassis ground.
  Connector and terminal
  
  (B65) No. 1 (+) - Chassis ground (-):
  
  Is the voltage 10 V or more?
  
  Yes : Go to 4 .
  
  No
  - Check fuse No. 37 (fuse and relay box).
  - Check for open or short circuit in harness between the stop light and brake switch and the fuse and relay box.
CHECK STOP LIGHT AND BRAKE SWITCH CIRCUIT .
Measure the voltage between connector terminal and chassis ground.

Connector and terminal

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

Is the voltage 10 V or more?

Yes : Go to 5 .

No
- Check fuse No. 19 (fuse and relay box).
- Check for open or short circuit in harness between the stop light and brake switch and the fuse and relay box.
CHECK STOP LIGHT AND BRAKE SWITCH CIRCUIT .
1. Turn the ignition switch to OFF.
2. Disconnect the ECM connector.
3. Measure the resistance between ECM connector terminal and stop light and brake switch connector terminal.
  Connector and terminal
  
  (B65) No. 4 - (B134) No. 36:
  
  (B65) No. 2 - (B134) No. 38:
  
  Is the resistance less than 10 Ω?
  
  Yes : Go to 6 .
  
  No : Repair the harness.
CHECK STOP LIGHT AND BRAKE SWITCH CIRCUIT .
1. Connect the stop light and 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 and terminal
  
  (B134) No. 36 (+) - Chassis ground (-):
  
  (B134) No. 38 (+) - Chassis ground (-):
  
  Does the voltage appear in (B134) No. 38 when the brake pedal is depressed? (0 V when the brake pedal is not depressed)
  
  Does the voltage appear in (B134) No. 36 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 and brake switch. Ref. to CRUISE CONTROL SYSTEM>STOP LIGHT AND BRAKE SWITCH .