Inspection Procedure 6: the ASC Warning Display Stays on Even After the Engine Is Started.

Inspection Procedure 6: The ASC warning display stays ON even after the engine is started.

CAUTION:
^ 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.

SYSTEM OPERATION
ASC-ECU sends the illumination request signal of ASC warning display to the combination meter through ETACS-ECU via CAN communication.

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 wiring harness and connectors
^ Malfunction of ETACS-ECU
^ Combination meter malfunction
^ ASC-ECU malfunction
^ Control stop due to the low voltage

NOTE: Due to the abnormality in the supply voltage, the diagnostic trouble code may not be set even when the ASC warning display 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 lines.
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. (Refer to Troubleshooting Can Bus Diagnostics Table.) Then go to Step 7.

STEP 2. Scan tool diagnostic trouble code
Using scan tool, check the diagnostic trouble code for ASC system.
Q: Is any DTC set?
YES: Carry out the diagnosis for the DTC. (Refer to Diagnostic Trouble Code Descriptions.)
NO: Go to Step 3.

STEP 3. Check of ASC-ECU power supply circuit
Refer to Inspection Procedure 11: ASC-ECU Power Supply Circuit System.
Q: Is the check result normal?
YES: Go to Step 4.
NO: Carry out the diagnosis of ASC-ECU power supply circuit system.(Refer to Inspection Procedure 11: ASC-ECU Power Supply Circuit System.)

STEP 4. Scan tool diagnostic trouble code for other system
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. (Refer to Combination Meter, Troubleshooting Combination Meter.) Then go to Step 7.
NO: Go to Step 5.

STEP 5. Scan tool diagnostic trouble code for other system
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. (Refer to ETACS, Troubleshooting ETACS.) Then go to Step 7.
NO: Go to Step 6.

STEP 6. Retest the system.
Q: Does the ASC warning display turn ON and OFF normally?
YES: Intermittent malfunction.
NO: Replace the hydraulic unit (incorporates in ASC-ECU). Then go to Step 7.

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