Inspection Procedure 3: Brake Warning Light Stays ON With the Parking Brake Lever Released
Inspection Procedure 3: Brake Warning Light Stays ON with the Parking Brake Lever Released.
CAUTION:
^ If there is any problem in the CAN bus lines, an incorrect diagnosis code may be set. Prior to this diagnosis, diagnose the CAN bus lines.
^ Whenever ECU is replaced, ensure that the CAN bus lines are normal.
OPERATION
^ When the parking brake switch is turned ON, the combination meter terminal No.4 is earthed, and the brake warning light illuminates.
^ When reduction of the brake fluid amount is detected, the brake fluid level switch is turned from ON to OFF. ETACS-ECU monitors the brake fluid level switch, and instructs the combination meter via the CAN bus line to illuminate the brake warning light.
TECHNICAL DESCRIPTION (COMMENT)
This may be caused by earth fault in the parking brake switch circuit.
PROBABLE CAUSES
^ The brake pad thickness is at the limit value or less.
^ The brake fluid amount is at the "LOWER" level or lower.
^ Poor adjustment of the parking brake lever
^ Damaged wiring harness and connectors
^ Parking brake switch malfunction
^ Brake fluid level switch malfunction
^ Combination meter malfunction
^ ETACS-ECU malfunction
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
STEP 1. M.U.T.-III CAN bus diagnostics
Use scan tool to diagnose the CAN bus lines.
Q: Is the check result normal?
YES: Go to Step 2.
NO: Repair the CAN bus lines.
STEP 2. M.U.T.-III diagnostic trouble code
Use scan tool to check that the diagnostic trouble code is set in the combination meter and ETACS-ECU.
Q: Is the DTC set?
YES: Carry out the diagnosis for the diagnostic trouble code.
NO: Go to Step 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?
YES: Go to Step
5.
NO: Go to Step 4.
STEP 4. Brake pad check
Q: Is the check result normal?
YES: Fill the brake fluid up to the "MAX" level. Then go to Step 18.
NO: Replace the brake pad. Then go to Step 18.
STEP 5. Brake fluid level switch check
Refer to BRAKE FLUID LEVEL SWITCH CHECK. Testing and Inspection
Q: Is the check result normal?
YES: Go to Step 6.
NO: Replace the reservoir tank assembly. Then go to Step 18.
STEP 6. Connector check: A-09 brake fluid level switch connector, C-312 ETACS-ECU connector
Q: Is the check result normal?
YES: Go to Step 7.
NO: Repair the damaged connector.
STEP 7. Measure the voltage at A-09 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 earth.
OK: Approximately battery voltage
Q: Is the check result normal?
YES: Go to Step 9.
NO: Go to Step 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-09 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 earth by backprobing.
OK: Approximately battery voltage
Q: Is the check result normal?
YES: Check the wiring harness between the C-312 ETACS-ECU connector terminal No. 1 and the A-09 brake fluid level switch connector terminal No. 1.
NO: Replace the ETACS-ECU. Then go to Step 18.
STEP 9. Wiring harness check: between A-09 brake fluid level switch connector and body earth
Check for open circuit in the harness wire between A-09 brake fluid level switch connector terminal No. 2 and body earth.
Q: Is the check result normal?
YES: Go to Step 10.
NO: Repair the wiring harness.
STEP 10. Parking brake lever stroke check
Q: Is the check result normal?
YES: Go to Step 11.
NO: Adjust the parking brake lever stroke. Then go to Step 18.
STEP 11. Parking brake switch check
Q: Is the check result normal?
YES: Go to Step 12.
NO: Replace the parking brake switch. Then go to Step 18.
STEP 12. Connector check: D-125 parking brake switch connector
Q: Is the check result normal?
YES: Go to Step 13.
NO: Repair the damaged connector.
STEP 13. Measure the voltage at D-125 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 earth.
OK: Approximately battery voltage
Q: Is the check result normal?
YES: Go to Step 17.
NO: Go to Step 14.
STEP 14. Connector check: C-03 combination meter connector, C-22 intermediate connector
Q: Is the check result normal?
YES: Go to Step 15.
NO: Repair the damaged connector.
STEP 15. Voltage measurement with C-03 combination meter connector
1) Release the parking brake lever (status that the lever is not operated).
2) Turn the ignition switch to the ON position.
3) Measure the voltage between terminal No. 4 and the body earth by backprobing without disconnecting the connector.
OK: Approximately battery voltage
Q: Is the check result normal?
YES: Repair the wiring harness between the C-03 combination meter connector terminal No. 4 and the D-125 parking brake switch connector.
NO: Go to Step 16.
STEP 16. Resistance measurement with C-03 combination meter connector
1) Disconnect D-125 parking brake switch connector.
2) Measure the resistance between terminal No. 4 and the body earth.
OK: No continuity
Q: Is the check result normal?
YES: Go to Step 17.
NO: Repair the wiring harness between the C-03 combination meter connector terminal No. 4 and the D-125 parking brake switch connector.
STEP 17. Retest the system.
Q: Does the brake warning light turn ON and OFF normally according to the parking brake lever operation?
YES: Intermittent malfunction.
NO: Replace the combination meter assembly. Then go to Step 18.
STEP 18. Retest the system.
Q: Does the brake warning light turn ON and OFF normally according to the parking brake lever operation?
YES: This diagnosis is complete.
NO: Return to Step 1.