Inspection Procedure 5

Inspection Procedure 5: ABS warning light stays ON after the engine is started.

CAUTION:

- If there is any problem in the CAN bus lines, an incorrect DTC may be set. Prior to this diagnosis, diagnose the CAN bus lines CAN Bus Diagnostics Chart ).
- Whenever ECU is replaced, ensure that the CAN bus lines are normal.

CIRCUIT OPERATION

- ABS-ECU sends the illumination request signal of the ABS warning light to the combination meter through ETACS-ECU via CAN communication.
- ABS-ECU illuminates the ABS warning light via ETACS-ECU for approximately 3 seconds for valve check with the ignition switch turned to the ON position.

COMMENTS ON TROUBLE SYMPTOM

This may be caused by faults in the CAN bus line, ETACS-ECU, combination meter or ABS-ECU.

PROBABLE CAUSES

- Damaged wiring harness and connectors
- Malfunction of ETACS-ECU
- Malfunction of combination meter
- Malfunction of ABS-ECU
NOTE:
Due to the abnormality in the supply voltage, the DTC may not be set even when the ABS warning light is illuminated.

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.

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 CAN Bus Diagnostics Chart).
Then go to Step 6.
STEP 2. Scan tool DTC

Use scan tool to check the DTC for the ABS system.

Q. Is the DTC set?

YES Carry out the diagnosis for the diagnostic trouble code (Refer to Anti-Lock Braking System (ABS)).
NO Go to Step 3.
STEP 3. Scan tool other system DTC

Using scan tool, check that the DTC U0141 is not set by the combination meter system.

Q. Is any DTC set?

YES Troubleshoot the combination meter Combination Meter), and then go to Step 6
.
NO Go to Step 4.
STEP 4. Scan tool other system DTC

Using scan tool, check that the DTC U0121 is not set by the ETACS system.

Q. Is any DTC set?

YES Perform troubleshooting on ETACS-ECU. Electronic Time and Alarm Control System (ETACS)).
Then go to Step 6.
NO Go to Step 5.
STEP 5. Retest the system.

Drive the vehicle more at 6 mph (10 km/h) or high.

Q. Does the ABS warning light turn ON and OFF normally?

YES Intermittent malfunction How to Cope With Intermittent Malfunctions).
NO Replace the hydraulic unit (integrated with ABS-ECU) (Refer to Anti-Lock Braking System (ABS)).
Then go to Step 6.
STEP 6. Retest the system.

Drive the vehicle more at 6 mph (10 km/h) or high.

Q. Does the ABS warning lamp turn ON and OFF normally?

YES The procedure is complete.
NO Return to Step 1.