Inspection Procedure 4: ABS Warning Light Does Not Illuminate When Ignition Switch Is Turned to the on Position (Engine Stopped

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 (Refer to Trouble code diagnosis Diagnostic Trouble Code Descriptions).
^ 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.

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 (Refer to Troubleshooting Diagnostic Trouble Code Descriptions).

STEP 2. Using scan tool MB991958, diagnostic trouble code
Use scan tool to check the diagnostic trouble code for the ASC system.
Q: Is the DTC set?
YES: Carry out the diagnosis for the diagnostic trouble code (Refer to Diagnostic Trouble Code Descriptions).
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. (Refer to Combination Meter, Actuator Test Table Scan Tool Testing and Procedures [Vehicles without color liquid crystal display] or [Vehicles with color liquid crystal display].)
Q: Is the check result normal?
YES: Go to Step 4.
NO: Diagnose the combination meter. (Refer to Combination Meter, Trouble Symptom Chart 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.
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, 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 (Refer to Troubleshooting Symptom Chart), 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
NO: Replace the hydraulic unit (ASC-ECU), 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.