4WD

DTC U0401: Engine CAN data error





CAUTION:
^ If there is any problem in the CAN bus lines, an incorrect DTC 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
AWD-ECU temporarily limits the AWD functions if an abnormality in the throttle opening angle signal is detected.

DTC SET CONDITIONS
If the following conditions are met when the system is in operation (always), AWD-ECU gradually switches the control from AWD to AWD AUTO, flashes the AWD/LOCK indicators alternately, and sets the DTC No. U0401.
^ IG1 voltage: 10 V or more
^ Throttle opening angle signal: More than 100%

TROUBLESHOOTING HINTS

Current trouble
^ Damaged wiring harness and connectors
^ Malfunction of accelerator pedal position sensor
^ Malfunction of crankshaft position sensor
^ Engine ECU malfunction
^ AWD-ECU malfunction

Past trouble
^ Refer to "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
^ MB991958: Scan Tool (M.U.T.-III Sub Assembly)
^ MB991824: Vehicle Communication Interface
^ MB991827: M.U.T.-III USB Cable
^ MB991910: M.U.T.-III Main Harness A

STEP 1. Scan tool MB991958 CAN bus diagnostics Use scan tool MB991958 to diagnose the CAN bus lines.
Q: Is the check result normal?
YES: Go to Step 2.
NO: Repair the CAN bus line. Then go to Step 2.

STEP 2. Scan tool MB991958 DTC of other systems
Check if a DTC related to the accelerator pedal position sensor system or the crank angle sensor system is set in the engine control system.
Q: Is the DTC set?
YES: Troubleshoot the engine control system.
NO: Go to Step 3.

STEP 3. Scan tool MB991958 DTC of other systems
Check if a DTC, which relates to the CAN communication-linked systems below, is set.
^ Meter
U0401: DTC of engine-related failure information

Q: Is the DTC set?
YES: Go to Step 4.
NO: Go to Step 7.

STEP 4. Check whether the DTC is reset.
Q: Is the DTC No. U0401 set?
YES: Replace the engine control module. Then go to Step 8.
NO: 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. Then 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-128 AWD-ECU connector
^ C-313, C-317 ETACS-ECU connector
Q: Are the connectors and terminals in good condition?
YES: Go to Step 6.
NO: Repair the connector(s) or terminal(s). Then go to Step 8.

STEP 6. Wiring harness check
Check the wiring harness between the C-128 AWD-ECU connector and the C-313 ETACS-ECU connector for damage or other problem.
Q: Is the wiring harness in good condition?
YES: Go to Step 7.
NO: Repair damage or other problem in the wiring harness. Then go to Step 8.

STEP 7. Check whether the DTC is reset.
1. Erase the DTC.
2. Turn the ignition switch from the LOCK (OFF) position to the ON position.
3. Depress the throttle pedal fully.
4. Check if the DTC is set.
Q: Is the DTC No. U0401 set?
YES: Replace AWD-ECU. Then go to Step 8.
NO: 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.

STEP 8. Check whether the DTC is reset.
Q: Is the DTC No. U0401 set?
YES: Diagnose again from Step 1.
NO: This diagnosis is complete.