Code No. U0401 Engine (CAN message)


caution
  • If there is any problem in the CAN bus lines, an incorrect diagnosis code may be set. Prior to this diagnosis, diagnose the CAN bus lines (Refer to GROUP 54C - CAN Bus Diagnostics Table ).
  • If diagnosis code No.U0401 is set in ASC-ECU, always diagnose the CAN bus line. If there is any fault in the CAN bus lines, an incorrect diagnosis code may be set. In this case, the set diagnosis code is not highly reliable.
  • Before replacing the ECU, ensure that the communication circuit is normal.

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

DIAGNOSIS CODE SET CONDITIONS
This diagnosis code is set when the engine-ECU malfunction has been detected.

PROBABLE CAUSES

  • Malfunction of engine system
  • Malfunction of engine-ECU
  • Malfunction of ASC-ECU
  • External noise interference

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnosis
Use M.U.T.-III to diagnose the CAN bus lines.

Q. 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. M.U.T.-III diagnosis code
Use M.U.T.-III to check that any diagnosis code other than the code No.U0401 is set in ASC-ECU.

Q. Is the diagnosis code set?
Troubleshoot the relevant diagnosis code, and then go to Step 5.
Go to Step 3

STEP 3. M.U.T.-III other system diagnosis code
Use M.U.T.-III to check that the diagnosis code is set by the engine-ECU.

Q. Is the diagnosis code set?
Troubleshoot the relevant diagnosis code, and then go to Step 5.
Go to Step 4

STEP 4. Check whether the diagnosis code is reset.
Erase the diagnosis code.

Q. Is diagnosis code No.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 diagnosis code is reset.
Erase the diagnosis code.

Q. Is diagnosis code No.U0401 set?
Return to Step 1.
This diagnosis is complete.