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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 (Refer to GROUP 54C - CAN Bus Line Diagnostic 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.
Is the check result normal?
Go to Step 2.
Repair the CAN bus lines. (Refer to GROUP 54C - CAN Bus Diagnostics Table ). 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.
Is any DTC set?
Troubleshoot the relevant diagnostic trouble code, and then go to Step 5.
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.
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.
Erase the DTC.
Is DTC U0401 set?
Replace the hydraulic unit (integrated with ASC-ECU) (Refer to ), and then go to Step 5.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/How to Cope with Intermittent Malfunctions ).
 
STEP 5. Check whether the DTC is reset.
Erase the DTC.
Is DTC U0401 set?
Return to Step 1.
The procedure is complete.