Code No. U0001: Bus Off


caution If diagnosis code U0001 is stored in the engine-ECU, surely perform CAN bus line diagnosis.
caution Replace ECU after certainly confirming that the communication circuits are normal.

TROUBLE JUDGEMENT


Check Condition
  • Always.
Judgement Criterion
  • Bus off error detected.
COMMENTS ON TROUBLE SYMPTOM
  • The failure is possibly caused by malfunction of the harness and connector in CAN bus line or by malfunction in engine-ECU.

FAIL-SAFE AND BACKUP FUNCTION



  • None

PROBABLE CAUSES



  • Failed harness and connector
  • Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnosis

  • Use M.U.T.-III to perform CAN bus line diagnosis.

Q. Is the check result normal?
Go to Step 2.
Repair CAN bus line (Refer to GROUP 54C - Troubleshooting - CAN Bus Diagnostics Table ). After repairing CAN bus line, go to Step 3.

STEP 2. M.U.T.-III diagnosis code

  • Reconfirmation of diagnosis code.
Confirm again the diagnosis code is set from the engine-ECU.

  1. Erase the set diagnosis code.
  2. Ignition switch: LOCK (OFF) → ON
  3. Confirm whether the diagnosis code is set.

Q. Is diagnosis code set?
After replacing the engine-ECU, go to Step 3.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).

STEP 3. M.U.T.-III diagnosis code

  • Reconfirmation of diagnosis code.
Confirm again the diagnosis code is set from the engine-ECU.

  1. Erase the set diagnosis code.
  2. Ignition switch: LOCK (OFF) → ON
  3. Confirm whether the diagnosis code is set.

Q. Is diagnosis code set?
Go to Step 1.
Check end.