Inspection Procedure 2: Brake Warning Lamp 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 (Refer to GROUP 54C, Trouble code diagnosis ).
  • Whenever ECU is replaced, ensure that the CAN bus lines are normal.

OPERATION

  • When the parking brake lever is pulled, the parking brake switch is turned from OFF to ON. ABS-ECU monitors the parking brake switch, and instructs the combination meter via the CAN bus line to illuminate the brake warning lamp.
  • When reduction of the brake fluid amount is detected, the brake fluid level switch is turned from OFF to ON. ABS-ECU monitors the brake fluid level switch, and instructs the combination meter via the CAN bus line to illuminate the brake warning lamp.

COMMENTS ON TROUBLE SYMPTOM
This may be caused by earth fault in the parking brake switch or brake fluid level 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
  • Malfunction of ABS-ECU

DIAGNOSTIC PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics
Use M.U.T.-III to diagnose the CAN bus lines.

Q. Is the check result normal?
Go to Step 2.
Repair the CAN bus lines. (Refer to GROUP 54C - CAN Bus Diagnosis table .)

STEP 2. M.U.T.-III diagnosis code
Use M.U.T.-III to check the diagnosis code for the ABS system.

Q. Is the diagnosis code set?
Carry out the diagnosis for the diagnosis code.
Go to Step 3.

STEP 3. M.U.T.-III actuator test
Perform the following actuator test by the combination meter system, and check if the brake warning lamp illuminates. (Refer to GROUP 54A - Combination Meter, Actuator Test Table .)

  • Item No.20: Indicator lamp 1

Q. Is the check result normal?
Go to Step 4.
Diagnose the combination meter. (Refer to GROUP 54A - Combination Meter, Trouble Symptom Chart <COLT> <COLT CZ3>.) Then go to Step 13.

STEP 4. Brake fluid level check
Check that the brake fluid is filled up to the "MIN" level or higher.

Q. Is the check result normal?
Go to Step 6.
Go to Step 5.

STEP 5. Brake pad check
Refer to GROUP 35A - On-vehicle Service, Brake Pad Check .

Q. Is the check result normal?
Fill the brake fluid up to the "MAX" level. Then go to Step 13.
Replace the brake pad. (Refer to GROUP 35A - On-vehicle Service, Brake Pad Replacement .) Then go to Step 13.

STEP 6. Connector check: A-04 brake fluid level switch connector, A-05 ABS-ECU connector, C-23 parking brake switch connector




Q. Is the check result normal?

Go to Step 7.

Repair the damaged connector. Then go to Step 13.

STEP 7. Measure the resistance at the A-05 ABS-ECU connector.

(1)Disconnect the ABS-ECU connector, connect special tool ABS check harness (MB991951) to the harness-side connector, and then measure the resistance at the special tool connector side.
note Do not connect the special tool ABS check harness (MB991951) to ABS-ECU.
(2)Disconnect the A-04 brake fluid level switch connector.

(3)Measure the resistance between the brake fluid level switch signal terminal No.3 and the body earth.
OK: No continuity

Q. Is the check result normal?

Go to Step 8.

The wiring harness between the A-04 brake fluid level switch connector terminal No. 2 and the A-05 ABS-ECU connector terminal No. 3 is short-circuited, thus repair it. Then go to Step 13.

STEP 8. Measure the resistance at the A-05 ABS-ECU connector.

(1)Disconnect the ABS-ECU connector, connect special tool ABS check harness (MB991951) to the harness-side connector, and then measure the resistance at the special tool connector side.
note Do not connect the special tool ABS check harness (MB991951) to ABS-ECU.
(2)Disconnect the C-23 parking brake switch connector.

(3)Measure the resistance between the parking brake switch signal terminal No.17 and the body earth.
OK: No continuity

Q. Is the check result normal?

Go to Step 9.

The wiring harness between the C-23 parking brake switch connector terminal No. 1 and the A-05 ABS-ECU connector terminal No. 17 is short-circuited, thus repair it. Then go to Step 13.

STEP 9. Brake fluid level switch check
Refer to GROUP 35A - On-vehicle Service, Brake Fluid Level Switch Check .

Q. Is the check result normal?
Go to Step 10.
Replace the reservoir tank assembly. (Refer to GROUP 35A - Master Cylinder Assembly · Brake Booster Assembly <LHD> <RHD>.) Then go to Step 13.

STEP 10. Parking brake lever stroke check
Refer to GROUP 36 - On-vehicle Service .

Q. Is the check result normal?
Go to Step 11.
Adjust the parking brake lever stroke. (Refer to GROUP 36 - On-vehicle Service .) Then go to Step 13.

STEP 11. Parking brake switch check
Refer to GROUP 36 - On-vehicle Service .

Q. Is the check result normal?
Go to Step 12.
Replace the parking brake switch. (Refer to GROUP 36 - Parking Brake Lever .) Then go to Step 13.

STEP 12. Retest the system.

Q. Does the brake warning lamp turn ON and OFF normally according to the parking brake lever operation?
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction .)
Replace the hydraulic unit (integrated with ABS-ECU) (Refer to ). Then go to Step 13.

STEP 13. Retest the system.

Q. Does the brake warning lamp turn ON and OFF normally according to the parking brake lever operation?
This diagnosis is complete.
Return to Step 1.