Inspection Procedure 2: Brake Warning Light Stays on With the Parking Brake Lever Released

Inspection Procedure 2: Brake Warning Light Stays ON with the Parking Brake Lever Released.








CAUTION
If there is any problem in the CAN bus lines, an incorrect diagnostic trouble code may be set. Prior to this diagnosis, diagnose the CAN bus lines.

CIRCUIT OPERATION
When the parking brake switch is turned ON, the combination meter terminal No.4 is grounded, and the brake warning light illuminates.

TECHNICAL DESCRIPTION (COMMENT)
This may be caused by ground fault in the parking brake switch circuit.

TROUBLESHOOTING HINTS (The most likely causes for this case:)
^ Low brake fluid level
^ Damaged wiring harness and connectors
^ Parking brake switch malfunction
^ Combination meter malfunction
^ Malfunction of ETACS-ECU
^ EBD system 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 A

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. On completion, go to Step 2.

STEP 2. Diagnostic trouble code check after resetting CAN bus lines
Q: Is any DTC set?
YES: Carry out the relevant troubleshooting.
NO: Go to Step 3.

STEP 3. Brake fluid level check
Q: Is the check result normal?
YES: Go to Step 4.
NO: Add brake fluid to the specified level.

STEP 4. Brake fluid level switch check
Q: Is the check result normal?
YES: Go to Step 5.
NO: Replace the reservoir assembly.

STEP 5. Voltage measurement at C-312 ETACS-ECU connector
^ Measure the voltage between the terminal No. 1 and body ground.
OK: Approximately 5 volts

Q: Is the check result normal?
YES: Go to Step 6.
NO: Replace ETACS-ECU.

STEP 6. Connector check: C-312 ETACS-ECU connector, A-06 brake fluid level switch connector
Q: Is the check result normal?
YES: Go to Step 7.
NO: Repair the defective connector.

STEP 7. Check the wiring harness between the C-312 ETACS-ECU connector terminal No.1 and the A-06 brake fluid level switch connector terminal No. 1.
Q: Is the check result normal?
YES: Go to Step 8.
NO: Check the wiring harness between the C-312 ETACS-ECU connector terminal No. 1 and the A-06 brake fluid level switch connector terminal No. 1.

STEP 8. Parking brake lever stroke check
Refer to On-vehicle Service.
Q: Is the check result normal?
YES: Go to Step 9.
NO: Adjust the parking brake lever stroke, then go to Step 12.

STEP 9. Parking brake switch check
Refer to On-vehicle Service.
Q: Is the check result normal?
YES: Go to Step 10.
NO: Replace the parking brake switch.

STEP 10. Voltage measurement at the C-04 combination meter connector
^ Measure the voltage between terminal No.4 and body ground.
OK: Approximately 5 volts

Q: Is the check result normal?
YES: Go to Step 11.
NO: Replace the combination meter assembly, then go to Step 12.

STEP 11. Connector check: C-04 Combination meter connector, C-21 intermediate connector, C-117 parking brake switch connector
Q: Is the check result normal?
YES: Repair the wiring harness between the C-04 combination meter connector terminal No.4 and the C-117 parking brake switch connector.
NO: Repair the defective connector.

STEP 12. Retest the system.
Q: Does the brake warning light turn ON and OFF normally according to the parking brake lever operation?
YES: The procedure is complete.
NO: Return to Step 1.