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Diagnostic Procedure

  1. STEP 1. Scan tool CAN bus diagnostics 

    Using scan tool MB991958, 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 TROUBLESHOOTING .) After repairing the CAN bus line, go to Step 2.
  2. STEP 2. Check whether the DTC is reset. 

    Q: Is DTC No. C1000 set? 

    1. YES:  Go to Step 3.
    2. NO:  This diagnosis is complete.
  3. STEP 3. Check of the stoplight on and off 

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

    Q: Is the check result normal? 

    1. YES:  Go to Step  16.
    2. NO:  Go to Step 4.
  4. STEP 4. Stop light switch installation status check 

    Refer to ON-VEHICLE SERVICE .

    Q: Is the check result normal? 

    1. YES:  Go to Step 5.
    2. NO:  Install the stop light switch correctly. Then go to Step  21.
  5. STEP 5. Check the stop light switch. 

    Refer to BRAKE PEDAL .

    Q: Is the check result normal? 

    1. YES:  Go to Step 6.
    2. NO:  Replace the stoplight switch. (Refer to BRAKE PEDAL .) Then go to Step  21.
  6. STEP 6. ETACS-ECU connector check: C-304 

    Q: Is the check result normal? 

    1. YES:  Go to Step 7.
    2. NO:  Repair the defective connector. Then go to Step  21.
  7. STEP 7. Measure the voltage at the C-304 ETACS-ECU connector. 

    With C-304 ETACS-ECU connector connected, measure the voltage between the terminal No. 1 and the body ground.

    OK: Battery voltage (when the brake pedal is released) 

    Q: Is the check result normal? 

    1. YES:  Go to Step  10.
    2. NO:  Go to Step 8.
  8. STEP 8. ETACS-ECU fuse No. 2 check 

    Q: Is the check result normal? 

    1. YES:  Replace the ETACS-ECU. (Refer to ETACS-ECU .) Then go to Step  21.
    2. NO:  Replace fuse No. 2. Then go to Step 9.
  9. STEP 9. Check the wiring harness between C-304 ETACS-ECU connector terminal No. 1 and C-48 stoplight switch connector terminal No. 2. 

    Check that the wiring harness is not shorted (short to ground).

    Q: Is the check result normal? 

    1. YES:  Go to Step  21.
    2. NO:  Repair the wiring harness. Then go to Step  21.
  10. STEP 10. Stop light switch connector check: C-48 

    Q: Is the check result normal? 

    1. YES:  Go to Step 11.
    2. NO:  Repair the defective connector. Then go to Step  21.
  11. STEP 11. Voltage measurement at the C-48 stoplight switch connector 

    Disconnect the connector, and measure the voltage between terminal No. 2 and ground at the wiring harness side.

    OK: Battery positive voltage 

    Q: Is the check result normal? 

    1. YES:  Go to Step  13.
    2. NO:  Go to Step 12.
  12. STEP 12. Check the wiring harness between C-304 ETACS-ECU connector terminal No. 1 and C-48 stoplight switch connector terminal No. 2. 

    Check the wiring harness for open circuit.

    Q: Is the check result normal? 

    1. YES:  Go to Step 13.
    2. NO:  Repair the wiring harness. Then go to Step  21.
  13. STEP 13. J/C (4), intermediate connector check: C-43, C-47 

    Q: Is the check result normal? 

    1. YES:  Go to Step 14.
    2. NO:  Repair the defective connector. Then go to Step  21.
  14. STEP 14. Voltage measurement at C-43 J/C (4) 

    Disconnect the connector, and measure the voltage between terminal No. 2 and ground at the wiring harness side.

    OK: Battery positive voltage (brake pedal depressed) 

    Q: Is the check result normal? 

    1. YES:  Go to Step  16.
    2. NO:  Go to Step 15.
  15. STEP 15. Check the wiring harness between C-48 stoplight switch connector terminal No. 1 and the C-43 J/C (4) terminal No. 2. 

    Check the wiring harness for open or short circuit (short to ground).

    Q: Is the check result normal? 

    1. YES:  Go to Step 16.
    2. NO:  Repair the wiring harness. Then go to Step  21.
  16. STEP 16. ETACS-ECU connector check: C-312 

    Q: Is the check result normal? 

    1. YES:  Go to Step 17.
    2. NO:  Repair the defective connector. Then go to Step  21.
  17. STEP 17. Measure the voltage at the C-312 ETACS-ECU connector. 

    Measure the voltage between C-312 ETACS-ECU connector terminal No. 16 and the body ground.

    • OK: 1 V or less (brake pedal released) 
    • OK: Battery positive voltage (brake pedal depressed) 

      Q: Is the check result normal? 

      1. YES:  Go to Step  19.
      2. NO:  Go to Step 18.
  18. STEP 18. Check the wiring harness between C-312 ETACS-ECU connector terminal No. 16 and C-48 stoplight switch connector terminal No. 1. 

    Check the wiring harness for open circuit.

    Q: Is the check result normal? 

    1. YES:  Go to Step 19.
    2. NO:  Repair the wiring harness. Then go to Step  21.
  19. STEP 19. Scan tool service data 

    Item No. 39: Stoplight switch (Refer to SERVICE DATA REFERENCE TABLE  .)

    Q: Is the check result normal? 

    1. YES:  Go to Step 20.
    2. NO:  Replace the ETACS-ECU. (Refer to ETACS-ECU .) Then go to Step  21.
  20. STEP 20. Check whether the DTC is reset. 

    Q: Is DTC No. C1000 set? 

    1. YES:  Replace the AWC-ECU. (Refer to AWC-ECU  .) Then go to Step 21.
    2. NO:  Intermittent malfunction. (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ).
  21. STEP 21. Check whether the DTC is reset. 

    Q: Is DTC No. C1000 set? 

    1. YES:  Return to Step  1.
    2. NO:  This diagnosis is complete.
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