Electronic Control AWD

DTC U0001: Bus-off 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 monitors the CAN C-bus off interruption, and if any abnormality occurs, it interrupts the system.

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 FWD, flashes the AWD/LOCK indicators alternately, and sets the DTC U0001.

- IG1 voltage: 10 V or more
- When CAN C-bus off interruption is detected

TROUBLESHOOTING HINTS

Current trouble

- Wiring harness or connector failure of CAN bus line
- AWD-ECU malfunction
Past trouble

- Intermittent wiring harness or connector failure
NOTE:
For diagnosis procedures, refer to "How to treat past trouble" How to Treat Past Trouble ).

DIAGNOSIS

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 CAN Bus Diagnostics Chart). Then go to Step 3.
STEP 2. 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)Check if the DTC is set.

Q. Is the DTC U0001 set?

YES Replace AWD-ECU (Refer to Service and Repair). Then go to Step 3
.
NO The trouble can be an intermittent malfunction such as loose connector fit, wiring harness open circuit How to Cope With Intermittent Malfunctions).
STEP 3. Check whether the DTC is reset.

Q. Is the DTC U0001 set?

YES Diagnose again from Step 1.
NO This diagnosis is complete.