Inspection Procedure 3

Inspection Procedure 3: The 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 diagnostic trouble code may be set. Prior to this diagnosis, diagnose the CAN bus lines Initial Inspection and Diagnostic Overview ).
- Whenever the ECU is replaced, ensure that the CAN bus lines are normal.
- When the hydraulic unit (integrated with ASC-ECU) is replaced, always perform the calibration of steering wheel sensor, G and yaw rate sensor, brake fluid pressure sensor, cut valve, and inlet valve (Refer to G and Yaw Rate Sensor Calibration , Testing and Inspection , Master Cylinder Brake Fluid Pressure Sensor Calibration , and Testing and Inspection ).

SYSTEM OPERATION

- ASC-ECU sends the illumination signal of ABS warning light to the combination meter through ETACS-ECU via CAN communication.
- When the ignition switch is turned ON, ASC-ECU illuminates the ABS warning light via ETACS-ECU for approximately 3 seconds for the purpose of bulb check.

TECHNICAL DESCRIPTION (COMMENT)

In the case of this trouble symptom, there may be a malfunction to the CAN bus line, ETACS-ECU, combination meter, or ASC-ECU.

PROBABLE CAUSES

- Damaged harness wires and connectors
- Malfunction of the ETACS-ECU
- Malfunction of the combination meter
- Malfunction of ASC-ECU
- Abnormality with ETACS-ECU coding data

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.

Using scan tool MB991958, 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 8.
STEP 2. Scan tool diagnostic trouble code

Using scan tool, check the diagnostic trouble code for ASC system.

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. M.U.T.-III actuator test

Perform the following actuator tests from the combination meter system to check if the ABS warning light is illuminated Actuator Test Reference Table).

- Item 07: Indicator1

Q. Is the check result normal?

YES Go to Step 4.
NO Carry out the diagnosis of the combination meter. Symptom Chart). Then go to Step 8.
STEP 4. Coding data check

Using the scan tool, check if there is any abnormality to the coding data stored in the ETACS-ECU Programming and Relearning).

Q. Is the check result normal?

YES Go to Step 5.
NO Replace the ETACS-ECU Electronic Time and Alarm Control System (ETACS)-ECU Removal and Installation). Then go to Step 8.
STEP 5. Scan tool diagnostic trouble code for other systems

Using scan tool MB991958, check if diagnostic trouble code No. U0141 is set by the combination meter system.

Q. Is the DTC set?

YES Diagnose the combination meter Combination Meter).
Then go to Step 8.
NO Go to Step 6.
STEP 6. Scan tool diagnostic trouble code for other systems

Using scan tool MB991958, check if diagnostic trouble code No. U0121 is set by ETACS system.

Q. Is the DTC set?

YES Diagnose the ETACS-ECU Electronic Time and Alarm Control System (ETACS).
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 Service and Repair). 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.