Code No. U0001 Bus off



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.
  • Whenever ECU is replaced, ensure that the CAN bus lines are normal.

OPERATION



  • Signals from the ECUs communicate with the electric power steering-ECU.

FUNCTION



  • The signals from the ECUs communicate with the electric power steering-ECU for motor control.

TROUBLE JUDGEMENT


Check Conditions
  • IG1 voltage: 10 V or more
Judgement Criterion
  • The signals from the ECUs cannot communicate (bus off), and the microcomputer determines that there is a problem in the system.
Fail Safe, Back Up Function
  • The electric power steering-ECU illuminates the electric power steering warning display, and sets the diagnosis code No. U0001 to limit assist operation.

PROBABLE CAUSES



  • Malfunction of CAN bus line
  • Malfunction of the electric power steering-ECU
  • Malfunction of the engine-ECU
  • Malfunction of the ETACS-ECU
  • Malfunction of the ABS-ECU <vehicles without ASC>
  • Malfunction of the ASC-ECU <vehicles with ASC>

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 3.
Repair the CAN bus lines (Refer to GROUP 54C - Troubleshooting ). On completion, go to Step 2.

STEP 2. Diagnosis code recheck after resetting CAN bus lines


(1)Erase the diagnosis code.
(2)Turn the ignition switch from the LOCK (OFF) position to the ON position.
(3)Check if the diagnosis code is set.

Q. Is the diagnosis codes U0001 set?

Go to Step 3.
This diagnosis is complete.

STEP 3. 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)Check if the diagnosis code is set.

Q. Is the diagnosis codes U0001 set?

Replace the electric power steering-ECU (Refer to ).Then go to Step 4.
Intermittent malfunction (Refer to GROUP 00 - How to Cope with Intermittent Malfunction ).

STEP 4. 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)Check if the diagnosis code is set.

Q. Is the diagnosis codes U0001 set?

Return to Step 1.
This diagnosis is complete.