Code No. U0401: Engine CAN data error

caution
  • If there is any problem in the CAN bus lines, an incorrect diagnosis code may be set. Prior to this diagnosis, always diagnose the CAN bus lines.
  • Before replacing the ECU, ensure that the communication circuit is normal.

OPERATION



DIAGNOSIS CODE SET CONDITIONS




  • IG1 voltage: 10 V or more
  • Throttle opening angle signal: More than 100%

PROBABLE CAUSES


Current trouble
  • Damaged wiring harness and connectors
  • Malfunction of accelerator pedal position sensor
  • Malfunction of crankshaft position sensor
  • Engine ECU malfunction
  • 4WD-ECU malfunction
Past trouble
  • Refer to "How to treat past trouble" (GROUP 00 - How to Treat Past Trouble ) for proceeding the diagnostics. Diagnose mainly wiring harness or connector failure between the engine ECU and the accelerator pedal position sensor or between the engine ECU and the crank angle sensor.

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics
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 line. (Refer to GROUP 54C - Troubleshooting .) Then go to Step 2.

STEP 2. M.U.T.-III Diagnosis code of other systems
Check if a diagnosis code related to the accelerator pedal position sensor system or the crank angle sensor system is set in the engine control system.

Q. Is the diagnosis code set?
Troubleshoot the engine control system. (Refer to GROUP 13A - Troubleshooting , GROUP 13C - Troubleshooting, GROUP 13D - Troubleshooting , GROUP 13E - Troubleshooting .)
Go to Step 3.

STEP 3. M.U.T.-III Diagnosis code of other systems
Check if a diagnosis code, which relates to the CAN communication-linked systems below, is set.

  • Meter
    U0401: Diagnosis code of engine-related failure information

Q. Is the diagnosis code set?
Go to Step 4.
Go to Step 7.

STEP 4. Check whether the diagnosis code is reset.

Q. Is the diagnosis code No. U0401 set?
Replace the engine-ECU. (Refer to GROUP 13A - Engine-ECU , GROUP 13C - Engine-ECU , GROUP 13D - Engine-ECU , GROUP 13E - Engine-ECU .) Then go to Step 8.
A poor connection, open circuit or other intermittent malfunction between the engine ECU and the accelerator pedal position sensor, or between the engine ECU and the crank angle sensor is suspected. (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ). Then go to Step 5.

STEP 5. Check the following connector:
Check the connectors below for improper engagement, terminal damage or terminal drawn in the connector case.

  • C-130 4WD-ECU connector
  • C-313, C-317 ETACS-ECU connector

Q. Are the connectors and terminals in good condition?
Go to Step 6.
Repair the connector(s) or terminal(s). Then go to Step 8.

STEP 6. Wiring harness check
Check the wiring harness between the C-130 4WD-ECU connector and the C-313 ETACS-ECU connector for damage or other problem.

Q. Is the wiring harness in good condition?
Go to Step 7.
Repair damage or other problem in the wiring harness. Then go to Step 8.

STEP 7. Check whether the diagnosis code is reset.
(1)Erase the diagnosis code.
(2)Turn the ignition switch from the LOCK (OFF) position to the ON position.
(3)Depress the throttle pedal fully.
(4)Check if the diagnosis code is set.

Q. Is the diagnosis code No. U0401 set?
Replace 4WD-ECU. (Refer to .) Then go to Step 8.
A poor connection, open circuit or other intermittent malfunction between the engine ECU and the accelerator pedal position sensor, or between the engine ECU and the crank angle sensor is suspected. (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).

STEP 8. Check whether the diagnosis code is reset.

Q. Is the diagnosis code No. U0401 set?
Diagnose again from Step 1.
This diagnosis is complete.