Inspection Procedure 2: Brake warning light stays ON with the parking brake lever released: 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

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

   Use scan tool to diagnose the CAN bus lines.

   Q: Is the check result normal? 

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

   Use scan tool to check that the DTC is set in the combination meter and ETACS-ECU.

   Q: Is any DTC set? 

   1. YES:  Carry out the diagnosis for the DTC.
   2. NO:  Go to Step 3.
3. STEP 3. Brake fluid level check 

   Check that the brake fluid is filled up to the "MIN" level or higher.

   Q: Is the check result normal? 

   1. YES:  Go to  Step 5.
   2. NO:  Go to Step 4.
4. STEP 4. Brake pad check 

   Refer to BRAKE PAD CHECK .

   Q: Is the check result normal? 

   1. YES:  Fill the brake fluid up to the "MAX" level. Then go to  Step 18.
   2. NO:  Replace the brake pad (Refer to BRAKE PAD REPLACEMENT ). Then go to  Step 18.
5. STEP 5. Brake fluid level switch check 

   Refer to BRAKE FLUID LEVEL SWITCH CHECK .

   Q: Is the check result normal? 

   1. YES:  Go to Step 6.
   2. NO:  Replace the reservoir tank assembly (Refer to MASTER CYLINDER ASSEMBLY AND BRAKE BOOSTER ). Then go to  Step 18.
6. STEP 6. Connector check: A-06 brake fluid level switch connector, C-312 ETACS-ECU connector 

   Q: Is the check result normal? 

   1. YES:  Go to Step 7.
   2. NO:  Repair the damaged connector.
7. STEP 7. Measure the voltage at A-06 brake fluid level switch connector. 
   1. Disconnect the connector, and measure at the wiring harness side.
   2. Turn the ignition switch to the "ON" position.
   3. Measure the voltage between the terminal No. 1 and the body ground.

      OK: Approximately system voltage 

   Q: Is the check result normal? 

   1. YES:  Go to  Step 10.
   2. NO:  Go to Step 8.
8. STEP 8. Measure the voltage at the C-312 ETACS-ECU connector. 
   CAUTION: With the C-312 ETACS-ECU connector kept connected, disconnect the A-06 brake fluid level switch connector.
   1. Turn the ignition switch to the "ON" position.
   2. 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 9.
   2. NO:  Replace the ETACS-ECU (Refer to ETACS-ECU ). Then go to  Step 18.
9. STEP 9. Wiring harness check: between A-06 brake fluid level switch connector and C-312 ETACS-ECU connector 

   Check for open circuit in the harness wire between A-06 brake fluid level switch connector terminal No. 1 and C-312 ETACS-ECU connector terminal No. 1.

   Q: Is the check result normal? 

   1. YES:  Go to  Step 16.
   2. NO:  Repair the wiring harness. Then go to  Step 18.
10. STEP 10. Wiring harness check: between A-06 brake fluid level switch connector and body ground 

    Check for open circuit in the harness wire between A-06 brake fluid level switch connector terminal No. 2 and body ground.

    Q: Is the check result normal? 

    1. YES:  Go to Step 11.
    2. NO:  Repair the wiring harness.
11. STEP 11. Parking brake lever stroke check 

    Refer to PARKING BRAKE LEVER STROKE CHECK AND ADJUSTMENT .

    Q: Is the check result normal? 

    1. YES:  Go to Step 12.
    2. NO:  Adjust the parking brake lever stroke (Refer to PARKING BRAKE LEVER STROKE CHECK AND ADJUSTMENT ). Then go to  Step 18.
12. STEP 12. Parking brake switch check 

    Refer to PARKING BRAKE SWITCH CHECK .

    Q: Is the check result normal? 

    1. YES:  Go to Step 13.
    2. NO:  Replace the parking brake switch (Refer to PARKING BRAKE LEVER ). Then go to  Step 18.
13. STEP 13. Connector check: C-117 parking brake switch connector 

    Q: Is the check result normal? 

    1. YES:  Go to Step 14.
    2. NO:  Repair the damaged connector.
14. STEP 14. Measure the voltage at C-117 parking brake switch connector. 
    1. Disconnect the connector, and measure at the wiring harness side.
    2. Turn the ignition switch to the "ON" position.
    3. Measure the voltage between the terminal No. 1 and the body ground.

       OK: Approximately system voltage 

    Q: Is the check result normal? 

    1. YES:  Go to  Step 17.
    2. NO:  Go to Step 15.
15. STEP 15. Connector check: C-04 Combination meter connector, C-22 intermediate connector 

    Q: Is the check result normal? 

    1. YES:  Go to Step 16.
    2. NO:  Repair the defective connector.
16. STEP 16. Wiring harness check: between the C-04 combination meter connector and the C-117 parking brake switch connector 

    Check for short circuit in the harness wire between the C-04 combination meter connector terminal No. 4 and the C-117 parking brake switch connector terminal No. 1.

    Q: Is the check result normal? 

    1. YES:  Go to Step 17.
    2. NO:  Repair the wiring harness. Then go to  Step 18.
17. STEP 17. Retest the system. 

    Q: Does the brake warning light turn ON and OFF normally according to the parking brake lever operation? 

    1. YES:  Intermittent malfunction (Refer to HOW TO COPE WITH INTERMITTENT MALFUNCTION ).
    2. NO:  Replace the combination meter assembly (Refer to COMBINATION METER ). Then go to Step 18.
18. STEP 18. Retest the system. 

    Q: Does the brake warning light turn ON and OFF normally according to the parking brake lever operation? 

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