Inspection Procedure 7: ASC Warning Display Stays ON After the Engine Is Started

Inspection Procedure 7: ASC Warning Display Stays ON After the Engine is Started.

CAUTION:
^ 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 ASC warning display to the combination meter through ETACS-ECU via the CAN communication.

TECHNICAL DESCRIPTION (COMMENT)
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
^ Control is disabled due to the low voltage

NOTE: Due to the abnormality in the supply voltage, the diagnosis code may not be set even when the ASC warning display illuminates.

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

STEP 1. M.U.T.-III CAN bus diagnostics
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.

STEP 2. M.U.T.-III diagnostic trouble code
Use scan tool to check the diagnostic trouble code for the ASC system.
Q: Is any DTC set?
YES: Carry out the diagnosis for the diagnostic trouble code.
NO: Go to Step 3.

STEP 3. Check the ASC-ECU power supply circuit system.
Refer to Inspection Procedure 12: ASC-ECU Power Supply Circuit System. Inspection Procedure 12: ASC-ECU Power Supply Circuit System
Q: Is the check result normal?
YES: Go to Step 4.
NO: Diagnose the power supply circuit of the ASC-ECU.

STEP 4. M.U.T.-III other system diagnostic trouble code
Using scan tool, check that the diagnostic trouble code U0141 is not set by the combination meter system.
Q: Is any DTC set?
YES: Diagnose the combination meter. Then go to Step 7.
NO: Go to Step 5.

STEP 5. M.U.T.-III other system diagnostic trouble code
Using scan tool, check that the diagnostic trouble code U0121 is not set by the ETACS system.
Q: Is any DTC set?
YES: Perform troubleshooting on ETACS-ECU. Then go to Step 7.
NO: Go to Step 6.

STEP 6. Retest the system.
Q: Does the ASC indicator light turn ON and OFF normally?
YES: Intermittent malfunction.
NO: Replace the ASC-ECU, and then go to Step 7.

STEP 7. Retest the system.
Q: Does the ASC indicator light turn ON and OFF normally?
YES: The procedure is complete.
NO: Return to Step 1.