Inspection Procedure 6

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 Initial Inspection and Diagnostic Overview ) 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 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 CAN Bus Diagnostics Chart).
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 Active Stability Control System (ASC)).
NO Go to Step 3.
STEP 3. Check of ASC-ECU power supply circuit

Refer to Inspection Procedure 12.

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 12).
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 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 Electronic Time and Alarm Control System (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 How to Cope With Intermittent Malfunctions).
NO Replace the hydraulic unit (integrated with ASC-ECU) (Refer to Service and Repair).
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.