Active Stability Control System (ASC)

DTC U0401: Engine malfunction detected

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.
- If diagnostic trouble code U0401 is set in ASC-ECU, always diagnose CAN bus lines. If there is any fault in the CAN bus lines, an incorrect DTC may be set.
- When the hydraulic unit (integrated with ASC-ECU) is replaced, after turning the ignition switch ON and OFF (vehicle information from ETACS-ECU is registered), 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 ).

CIRCUIT OPERATION

Engine-related signals are sent or received to and from between ASC-ECU and ECM via CAN bus lines.

DTC SET CONDITIONS

This diagnostic trouble code is set when the ECM malfunction has been detected.

PROBABLE CAUSES

- Malfunction of engine system
- ECM malfunction
- ASC-ECU malfunction
- External noise interference

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.) After repairing the CAN bus line, go to Step 5.
STEP 2. Scan tool diagnostic trouble code

Using scan tool MB991958, check if any diagnostic trouble code other than code No. U0401 is set in ASC-ECU.

Q. Is any DTC set?

YES Troubleshoot the relevant diagnostic trouble code, and then go to Step 5.
NO Go to Step 3.
STEP 3. Diagnostic trouble code check of other system using scan tool MB991958

Using scan tool MB991958, check if a diagnostic trouble code is set in the engine control module.

Q. Is any DTC set?

YES Troubleshoot the relevant diagnostic trouble code, and then go to Step 5.
NO Go to Step 4.
STEP 4. Check whether the DTC is reset.

Erase the DTC.

Q. Is DTC U0401 set?

YES Replace the hydraulic unit (integrated with ASC-ECU) (Refer to Service and Repair).
Then go to Step 5.
NO Intermittent malfunction. How to Cope With Intermittent Malfunctions).
STEP 5. Check whether the DTC is reset.

Erase the DTC.

Q. Is DTC U0401 set?

YES Return to Step 1.
NO The procedure is complete.