Inspection Procedure 3

Inspection Procedure 3: Brake Warning Light Stays ON with the Parking Brake Lever Released.





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

TECHNICAL DESCRIPTION (COMMENT)
The following cases may have occurred.
^ Ground fault in the parking brake switch circuit.
^ The EBD is defective.
^ The brake fluid level in the brake fluid reservoir is the specified value or lower.

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
^ Malfunction of EBD

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. Brake fluid level check
Q: Is the check result normal?
YES: Go to Step 2.
NO: Add brake fluid to the specified level.

STEP 2. Brake fluid level switch check
Q: Is the check result normal?
YES: Go to Step 3.
NO: Replace the reservoir assembly and master cylinder assembly.

STEP 3. Voltage measurement at C-312 ETACS-ECU connector





^ Measure the voltage between the terminal No. 1 and the body ground.
OK: Approximately 5 volts

Q: Is the check result normal?
YES: Go to Step 4.
NO: Replace ETACS-ECU.

STEP 4. Connector check: C-312 ETACS-ECU connector, A-09 brake fluid level switch connector
Q: Is the check result normal?
YES: Go to Step 5.
NO: Repair the defective connector.

STEP 5. 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.
Q: Is the check result normal?
YES: Go to Step 6.
NO: 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.

STEP 6. Parking brake lever stroke check
Q: Is the check result normal?
YES: Go to Step 7.
NO: Adjust the parking brake lever stroke, and then go to Step 10.

STEP 7. Parking brake switch check
Q: Is the check result normal?
YES: Go to Step 8.
NO: Replace the parking brake switch.

STEP 8. Voltage measurement at the C-03 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 9.
NO: Replace the combination meter assembly, and then go to Step 10.

STEP 9. Connector check: C-03 Combination meter connector, C-22 intermediate connector, D-125 parking brake switch connector
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: Repair the defective connector.

STEP 10. 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.