DTC C1000: Abnormality in stop light switch circuit: Diagnosis

Required Special Tools: 

• MB991958: Scan Tool (M.U.T.-III Sub Assembly)
  • MB991824: Vehicle Communication Interface (V.C.I.)
  • MB991827: M.U.T.-III USB Cable
  • MB991910: M.U.T.-III Main Harness A
• MB991974: ABS check harness

1. STEP 1. Using scan tool MB991958, diagnose the CAN bus lines. 

   Use scan tool to diagnose the CAN bus lines.

   Q: Is the check result normal? 

   1. YES:  Go to  Step 3.
   2. NO:  Repair the CAN bus lines (Refer to CAN BUS DIAGNOSTICS TABLE ). On completion, go to Step 2.
2. STEP 2. DTC recheck after resetting CAN bus lines 

   Q: Is DTC C1000 set? 

   1. YES:  Go to Step 3.
   2. NO:  The procedure is complete.
3. STEP 3. Battery check 

   Refer to BATTERY TEST .

   Q: Is the battery in good condition? 

   1. YES:  Go to Step 4.
   2. NO:  Charge or replace the battery, and go to  Step 17.
4. STEP 4. Stoplight operation check 

   Check the stoplight operation when the brake pedal is depressed. Check that the stoplight illuminates when the brake pedal is depressed and that it goes out when the brake pedal is released.

   OK: 

   When the brake pedal is released: OFF 

   When the brake pedal is depressed: Illuminates 

   Q: Is the check result normal? 

   1. YES:  Go to  Step 18.
   2. NO:  Go to Step 5.
5. STEP 5. Check stoplight switch installation 

   Refer to BRAKE PEDAL CHECK AND ADJUSTMENT .

   Q: Is the check result normal? 

   1. YES:  Go to Step 6.
   2. NO:  Install the stop light switch correctly (Refer to BRAKE PEDAL CHECK AND ADJUSTMENT ). Then go to  Step 22.
6. STEP 6. Stop light switch continuity check 
   1. Remove the stop light switch (Refer to BRAKE PEDAL ).
   2. Connect the circuit tester (Ω range) to the stop light switch connector terminals No. 1 and 2.
   3. When no continuity is detected with the plunger pressed from the edge of the outer case by the dimension shown in illustration and when continuity is detected with the plunger released, the stop light switch is in good condition.

   Q: Is the check result normal? 

   1. YES:  Go to Step 7.
   2. NO:  Replace the stop light switch (Refer to BRAKE PEDAL ). Then go to  Step 22.
      Fig 1: Checking Stop Light Switch Continuity

      Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
7. STEP 7. ETACS-ECU fuse No. 2 check 

   Q: Is the check result normal? 

   1. YES:  Go to  Step 12.
   2. NO:  Go to Step 8.
8. STEP 8. Connector check: C-304 ETACS-ECU connector, C-312 ETACS-ECU connector, C-32 stoplight switch connector, C-39 Intermediate connector, D-11 Intermediate connector, D-14 Intermediate connector, F-23 Intermediate connector, F-06 rear combination light (stoplight: RH) connector, F-20 rear combination light (stoplight: LH) connector, F-10 high-mounted stoplight connector 

   Q: Is the check result normal? 

   1. YES:  Go to Step 9.
   2. NO:  Repair the damaged connector, and then replace fuse No. 2. Then go to  Step 22.
9. STEP 9. Resistance measurement at C-32 stoplight switch connector 
   1. Disconnect C-32 stoplight switch connector, and measure at the wiring harness side.
   2. Disconnect C-312 ETACS-ECU connector and C-39 joint connector.
   3. Measure the resistance between the terminal No. 1 and the body ground.

      OK: No continuity 

   Q: Is the check result normal? 

   1. YES:  Go to Step 10.
   2. NO:  A short circuit may be present in the wiring harness between C-39 joint connector terminal No. 9 and C-32 stoplight switch connector terminal No. 1 or between C-312 ETACS-ECU connector terminal No. 16 and C-32 stoplight switch connector terminal No. 1. Repair the wiring harness if necessary, and then replace fuse No. 2. Then go to  Step 22.
10. STEP 10. Resistance measurement at C-32 stoplight switch connector 
    1. Disconnect C-32 stoplight switch connector, and measure at the wiring harness side.
    2. Disconnect C-304 ETACS-ECU connector.
    3. Measure the resistance between the terminal No. 2 and the body ground.

       OK: No continuity 

    Q: Is the check result normal? 

    1. YES:  Go to Step 11.
    2. NO:  A short circuit may be present in the wiring harness between C-304 ETACS-ECU connector terminal No. 1 and C-32 stoplight switch connector terminal No. 2. Repair the wiring harness if necessary, and then replace fuse No. 2. Then go to  Step 22.
11. STEP 11. Resistance measurement at C-39 joint connector 
    1. Disconnect C-39 joint connector, and measure at the wiring harness side.
    2. Disconnect F-06 rear combination light (stoplight: RH) connector, F-20 rear combination light (stoplight: LH) connector, F-10 high-mounted stoplight connector.
    3. Measure the resistance between the terminal No. 9 and the body ground.

       OK: No continuity 

    Q: Is the check result normal? 

    1. YES:  Replace fuse No. 2. Then go to  Step 22.
    2. NO:  A short circuit may be present in the wiring harness between C-39 joint connector terminal No. 9 and F-06 rear combination light (stoplight: RH) connector terminal No. 4 or between C-39 joint connector terminal No. 9 and F-20 rear combination light (stoplight: LH) connector terminal No. 4 or between C-39 joint connector terminal No. 9 and F-10 high-mounted stoplight connector terminal No. 1. Repair the wiring harness if necessary, and then replace fuse No. 2. Then go to  Step 22.
12. STEP 12. Connector check: C-304 ETACS-ECU connector 

    Q: Is the check result normal? 

    1. YES:  Go to Step 13.
    2. NO:  Repair the damaged connector. Then go to  Step 22.
13. STEP 13. Measure the voltage at the C-304 ETACS-ECU connector. 
    CAUTION: Measure while the brake pedal is not depressed.

    Measure the voltage between terminal No. 1 and the body ground by backprobing.

    OK: Approximately system voltage 

    Q: Is the check result normal? 

    1. YES:  Go to Step 14.
    2. NO:  Replace the ETACS-ECU (Refer to ETACS-ECU ). Then go to  Step 22.
14. STEP 14. Connector check: C-32 Stoplight switch connector 

    Q: Is the check result normal? 

    1. YES:  Go to Step 15.
    2. NO:  Repair the damaged connector. Then go to  Step 22.
15. STEP 15. Measure the voltage at C-32 stoplight switch connector. 
    1. Disconnect C-32 stoplight switch connector, and measure the voltage at harness connector side.
    2. Measure the voltage between the terminal No. 2 and the body ground.

       OK: Approximately system voltage 

    Q: Is the check result normal? 

    1. YES:  Go to Step 16.
    2. NO:  An open circuit may be present in the wiring harness between C-304 ETACS-ECU connector terminal No. 1 and C-32 stoplight switch connector terminal No. 2. Repair the wiring harness. Then go to  Step 22.
16. STEP 16. Connector check: C-39 joint connector 

    Q: Is the check result normal? 

    1. YES:  Go to Step 17.
    2. NO:  Repair the damaged connector. Then go to  Step 22.
17. STEP 17. Voltage measurement at C-39 joint connector 
    CAUTION: Measure while the brake pedal is depressed.
    1. Disconnect the connector, and measure at the wiring harness side.
    2. Measure the voltage between the terminal No. 9 and the body ground.

       OK: Approximately system voltage 

    Q: Is the check result normal? 

    1. YES:  Go to Step 18.
    2. NO:  An open circuit may be present in the wiring harness between C-39 joint connector terminal No. 9 and C-32 stoplight switch connector terminal No. 1. Repair the wiring harness. Then go to  Step 22.
18. STEP 18. Connector check: C-312 ETACS-ECU connector 

    Q: Is the check result normal? 

    1. YES:  Go to Step 19.
    2. NO:  Repair the damaged connector. Then go to  Step 22.
19. STEP 19. Measure the voltage at the C-312 ETACS-ECU connector. 
    1. Measure by backprobing without disconnecting the connector.
    2. Measure the voltage between the terminal No. 16 and the body ground.

       OK: 

       When the brake pedal is released: 0 V - 5V (pulse) 

       When the brake pedal is depressed: Approximately system voltage 

    Q: Is the check result normal? 

    1. YES:  Go to  Step 21.
    2. NO:  Go to Step 20.
20. STEP 20. Check the wiring harness between C-312 ETACS-ECU connector terminal No. 16 and C-32 stoplight switch connector terminal No. 1 
    • Check the signal line for open circuit.

    Q: Is the check result normal? 

    1. YES:  Replace the ETACS-ECU.
    2. NO:  Repair the wiring harness.
21. STEP 21. Check whether the DTC is reset. 

    Erase the DTC.

    Q: Is DTC 1000 set? 

    1. YES:  Replace the hydraulic unit (integrated with ABS-ECU) (Refer to HYDRAULIC UNIT  ). Then go to Step 22.
    2. NO:  Intermittent malfunction (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTIONS ).
22. STEP 22. Check whether the DTC is reset. 

    Erase the DTC.

    Q: Is DTC 1000 set? 

    1. YES:  Return to  Step 1.
    2. NO:  The procedure is complete.