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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.
  • 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 , , , and .)

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?
Go to Step 2.
Repair the CAN bus lines. (Refer to GROUP 54C - Troubleshooting .) 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?
Troubleshoot the relevant diagnostic trouble code, and then go to Step 5.
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?
Troubleshoot the relevant diagnostic trouble code, and then go to Step 5.
Go to Step 4.

STEP 4. Check whether the DTC is reset.

Q. Is DTC U0401 set?
Replace the hydraulic unit (incorporates in ASC-ECU).(Refer to .) Then go to Step 5.
Intermittent malfunction. (Refer to GROUP 00 - How to Cope with Intermittent Malfunction .)

STEP 5. Check whether the DTC is reset.

Q. Is DTC U0401 set?
Return to Step 1.
The procedure is complete.