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

4WD-ECU temporarily limits the 4WD functions if an abnormality in the throttle opening angle signal is detected.

DIAGNOSIS CODE SET CONDITIONS

If the following conditions are met when the system is in operation (always), 4WD-ECU gradually switches the control from 4WD to 4WD AUTO, flashes the 4WD/LOCK indicators alternately, and sets the diagnosis code No. U0401.

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.