Diagnostic Procedure with ECU 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:

EyeSight system Ref. to WIRING SYSTEM>EyeSight 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 & BRAKE SWITCH .
Check the stop light & brake switch. Ref. to BRAKE>STOP LIGHT 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.
CHECK STOP LIGHT & BRAKE SWITCH CIRCUIT .
1. Turn the ignition switch to OFF.
2. Disconnect the ground terminal from battery sensor. Ref. to REPAIR CONTENTS>NOTE>BATTERY .
3. Disconnect the stop light & brake switch connector.
4. Using a tester, measure the resistance between the connector terminal and chassis ground.
  Connector & 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 & BRAKE SWITCH CIRCUIT .
1. Connect the ground terminal to battery sensor. Ref. to REPAIR CONTENTS>NOTE>BATTERY .
2. Turn the ignition switch to ON.
3. Measure the voltage between connector terminal and chassis ground.
  Connector & terminal
  
  (B65) No. 1 (+) - Chassis ground (-):
  
  Is the voltage 10 V or more?
  
  Yes : Go to 4.
  
  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.
CHECK STOP LIGHT & BRAKE SWITCH CIRCUIT .
Measure the voltage between connector terminal and chassis ground.

Connector & terminal

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

Is the voltage 10 V or more?

Yes : Go to 5.

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.
CHECK STOP LIGHT & 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 & brake switch connector terminal.
  Connector & terminal
  
  (B65) No. 4 - (B134) No. 35:
  
  (B65) No. 2 - (B134) No. 20:
  
  Is the resistance less than 10 Ω?
  
  Yes : Go to 6.
  
  No : Repair the harness.
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. 35 (+) - Chassis ground (-):
  
  (B134) No. 20 (+) - Chassis ground (-):
  
  Does the voltage appear in (B134) No. 20 when the brake pedal is depressed? (0 V when the brake pedal is not depressed)
  
  Does the voltage appear in (B134) No. 35 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) (H4DOTC)>Engine Control Module (ECM)>REMOVAL
  
  No : Replace the stop light & brake switch. Ref. to BRAKE>STOP LIGHT SWITCH .