Inspection Procedure 4

Inspection Procedure 4: ABS warning light does not illuminate when ignition switch is turned to the ON position (engine stopped).

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 Line Diagnostics Flow).

- Whenever ECU is replaced, ensure that the CAN bus lines are normal.

- When the hydraulic unit (integrated with ASC-ECU) is replaced, always carry out the calibration of the steering wheel sensor, the G and yaw rate sensor and brake fluid pressure sensor (Refer to Testing and Inspection, Testing and Inspection and Testing and Inspection).

OPERATION

- ASC-ECU sends the illumination request signal of the ABS warning light to the combination meter through ETACS-ECU via CAN communication.

- ASC-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 ASC-ECU.

PROBABLE CAUSES

- Damaged wiring harness and connectors

- Malfunction of ETACS-ECU

- Combination meter malfunction

- ASC-ECU malfunction

- Malfunction of coding data for ETACS-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 lines.

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).
STEP 2. Using scan tool MB991958, diagnostic trouble code

Use scan tool to check the diagnostic trouble code for the ASC system (Refer to Active Stability Control System (ASC)).

Q. Is the DTC set?

YES Carry out the diagnosis for the diagnostic trouble code (Refer to Active Stability Control System (ASC)).
NO Go to Step 3.
STEP 3. Using scan tool MB991958, actuator test

Perform the actuator test No.07 of the combination meter system, and check if the ABS warning light illuminates Actuator Test Reference Table).

Q. Is the check result normal?

YES Go to Step 4.
NO Diagnose the combination meter Symptom Chart). Then go to Step 8.
STEP 4. ETACS-ECU coding data check

Use scan tool to check if coding data stored in ETACS-ECU is normal Coding List).

Q. Is the check result normal?

YES Go to Step 5.
NO Replace the ETACS-ECU, and then go to Step 8.
STEP 5. Using scan tool MB991958, other system diagnostic trouble code

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

Q. Is the DTC U0141 set?

YES Troubleshoot the combination meter Combination Meter), and then go to Step 8
.
NO Go to Step 6.
STEP 6. Using scan tool MB991958, other system diagnostic trouble code

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

Q. Is the DTC U0121 set?

YES Troubleshoot the ETACS-ECU Electronic Time and Alarm Control System (ETACS)), and then go to Step 8.
NO Go to Step 7.
STEP 7. Retest the system.

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 ASC-ECU) (Refer to Active Stability Control System (ASC)), and then go to Step 8.
STEP 8. Retest the system.

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

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