Code No.U0019 Bus off (CAN-B)

  • If there is any problem in the CAN bus lines, an incorrect diagnosis code may be set. Prior to this diagnosis, always diagnose the CAN bus lines.
  • Before replacing the hands free-ECU, be sure to check that the power supply circuit, earth circuit, and communication circuit are normal.


When the hands free-ECU is returned from the bus off state, or when the bus error is indicated to the hands free-ECU state, the diagnosis code U0019 (CAN-B) is set.


The hands free-ECU, power supply for the hands free-ECU, earth circuit, or CAN bus line may have a problem.


  • Malfunctions of the hands free-ECU
  • Malfunction of CAN bus line wiring harness and connector


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 line.

STEP 2. Check whether the diagnosis code is reset.

Check again if the diagnosis code is set to the hands free-ECU.
(1)Erase the diagnosis code.
(2)Turn the ignition switch from "LOCK" (OFF) position to "ON" position.
(3)Check if diagnosis code is set.

Q. Is the diagnosis code set?

Replace the hands free-ECU.
The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).