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 CAN Bus Line Diagnostics Flow ).
- If diagnostic trouble code U0401 is set in ASC-ECU, always diagnose the CAN bus line. If there is any fault in the CAN bus lines, an incorrect diagnostic trouble code may be set. In this case, the set diagnostic trouble code is not highly reliable.
- Before replacing the ECU, ensure that the communication circuit is normal.

CIRCUIT OPERATION

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

DTC SET CONDITIONS

This diagnostic trouble code is set when the engine control module malfunction has been detected.

PROBABLE CAUSES

- Malfunction of engine system
- Engine control module malfunction
- ASC-ECU malfunction
- External noise interference

DIAGNOSIS

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. CAN Bus Diagnostics Chart).
On completion, go to Step 5.
STEP 2. Using scan tool MB991958, DTC

Use scan tool to check that any diagnostic trouble code other than the code 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. Using scan tool MB991958, other system DTC

Use scan tool to check that the diagnostic trouble code is set by 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), and 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.