Inspection Procedure 6: The Brake Warning Light Remains Illuminated After the Engine Is Started

INSPECTION PROCEDURE 6: The brake warning light remains illuminated after the engine is started.

TECHNICAL DESCRIPTION (COMMENT)
^ The brake warning light is used as the brake fluid level switch warning light, therefore, if the brake fluid level becomes lower than the specified, the brake fluid level switch is ON and the combination meter illuminates the brake warning light.
^ The brake warning light is used as the parking brake switch warning light, therefore, the parking brake switch is ON when the parking brake lever is pulled and the combination meter illuminates the brake warning light.

NOTE: The brake warning light is used as EBD warning light.

TROUBLESHOOTING HINTS (THE MOST LIKELY CAUSES FOR THIS CASE:)
^ 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 or connector
^ Combination meter defective
^ Malfunction of the brake fluid level switch
^ Malfunction of the parking brake switch
^ Malfunction of the hydraulic unit (integrated with ABS-ECU)

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

CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958, Use scan tool MB991958 to check whether combination meter DTC has been set.

1) Connect scan tool MB991958 to the data link connector.
2) Turn the ignition switch to the "ON" position.
3) Check whether combination meter DTC has been set.

Q: Is any DTC set? YES: Carry out the diagnosis for DTC.
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
Refer to On-vehicle Service, Brake Pad Check.

Q: Is the check result normal?
YES: Fill the brake fluid up to the "MAX" level. Then go to Step 15.
NO: Replace the brake pad. Then go to Step 15.

STEP 5. Brake fluid level switch check
Refer to On-vehicle Service, Brake Fluid Level Switch Check.

Q: Is the check result normal?
YES: Go to Step 6.
NO: Replace the reservoir tank assembly. Then go to Step 15.

STEP 6. Parking brake lever stroke check
Refer to On-vehicle Service.

Q: Is the check result normal?
YES: Go to Step 7.
NO: Adjust the parking brake lever stroke. Then go to Step 15.

STEP 7. Parking brake switch check
Refer to On-vehicle Service.

Q: Is the check result normal?
YES: Go to Step 8.
NO: Replace the parking brake switch. Then go to Step 15.

STEP 8. Connector check: A-103 intermediate connector, B-07 brake fluid level switch connector, C-01 joint connector, C-18 parking brake switch connector, C-29 intermediate connector and C101 combination meter connector

Q: Is the check result normal?
YES: Go to Step 9.
NO: Repair the damaged connector.

STEP 9. Measure the voltage at C-101 combination meter connector.

CAUTION:
^ Disconnect B-07 brake fluid level switch connector with C-101 combination meter connector connected.
^ Ensure that the parking brake lever is not pulled.

1) Turn the ignition switch to the ON position.

2) Measure the voltage between terminal No. 7 and the body ground by backprobing.
OK: Approximately battery voltage

Q: Is the check result normal?
YES: Go to Step 13.
NO: Go to Step 10.

STEP 10. Check the ground short at C-01 joint connector.
1) Disconnect A- 13 intermediate connector, C-29 intermediate connector and C-18 parking brake switch connector.
2) Measure at the C-01 joint connector side.

3) Check the continuity between terminal No. 28 and body ground.
OK: No continuity

Q: Is the check result normal?
YES: Go to Step 11.
NO: Repair the wiring harness between C-01 joint connector terminal No. 28 and C-18 parking brake switch connector terminal No. 1.

STEP 11. Check the ground short at C-01 joint connector.
1) Disconnect B-07 brake fluid level switch connector, C-29 intermediate connector and C-18 parking brake switch connector.
2) Measure at the C-01 joint connector side.

3) Check the continuity between terminal No. 27 and body ground.
OK: No continuity

Q: Is the check result normal?
YES: Go to Step 12.
NO: Repair the wiring harness between C-01 joint connector terminal No. 27 and B-07 brake fluid level switch connector terminal No. 1.

STEP 12. Check the ground short at C-01 joint connector.
1) Disconnect A-1 3 intermediate connector, C-18 parking brake switch connector and C-101 combination meter connector.
2) Measure at the C-01 joint connector side.

3) Check the continuity between terminal No. 26 and body ground.
OK: No continuity

Q: Is the check result normal?
YES: Go to Step 13.
NO: Repair the wiring harness between C-01 joint connector terminal No. 26 and C-101 combination meter connector terminal No. 7.

STEP 13. Retest the system

Q: Does the brake warning lamp 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 14.

STEP 14. Retest the system

Q: Does the brake warning lamp turn ON and OFF normally according to the parking brake lever operation?
YES: This diagnosis is complete.
NO: Replace the hydraulic unit (integrated with ABS-ECU). Then go to Step 15.

STEP 15. Retest the system

Q: Does the brake warning lamp turn ON and OFF normally according to the parking brake lever operation?
YES: This diagnosis is complete.
NO: Return to Step 1.