Code No. U0019: Bus off (CAN-B)


caution If diagnosis code No.U0019 is set in the A/C-ECU, diagnose the CAN main bus line.
caution Whenever the ECU is replaced, ensure that the communication circuit is normal.

TROUBLE JUDGMENT
If the A/C-ECU ceases communicating once (i.e. bus off) and then returns to it, the A/C-ECU will not communicate for three minutes immediately after that point. This three-minute period is called "Penalty mode." Immediately after the A/C-ECU returns to communication, the diagnosis code is set.

COMMENTS ON TROUBLE SYMPTOM
The wiring harness wire or connectors may have loose, corroded, or damage terminals, or terminals pushed back in the connector, or the A/C-ECU may be defective.

PROBABLE CAUSES

  • Damaged harness wires and connectors
  • Malfunction of the A/C-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics
Use the M.U.T.-III to diagnose the CAN bus lines.

Q. Is the check result normal?
Go to Step 2
Repair the CAN bus lines (Refer to GROUP 54C - Troubleshooting ). On completion, go to Step 3.

STEP 2. M.U.T.-III diagnosis code.
Recheck if the diagnosis code is set.
(1)Erase the diagnosis code.
(2)Ignition switch: LOCK (OFF) to ON
(3)Check if the diagnosis code is set.

Q. Is the diagnosis code set?
Replace the A/C-ECU, and then go to Step 3.
If a trouble is solved, it is determined that there is an intermittent malfunction such as poor engaged connector(s) or open circuit (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).

STEP 3. M.U.T.-III diagnosis code
Recheck if the diagnosis code is set.
(1)Erase the diagnosis code.
(2)Ignition switch: LOCK (OFF) to ON
(3)Check if the diagnosis code is set.

Q. Is the diagnosis code set?
Return to Step 1.
The procedure is complete.