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 audio unit, be sure to check that the power supply circuit,
earth circuit, and communication circuit are normal.
TROUBLE JUDGMENT
When the audio unit is returned from the bus off state, or when the bus error is indicated
to the audio unit state, the diagnosis code U0019 (CAN-B) is set.
COMMENTS ON TROUBLE SYMPTOM
The audio unit, power supply for the audio unit, earth circuit, or CAN bus line may have
a problem.
PROBABLE CAUSES
Malfunctions of audio unit
Malfunction of CAN bus line wiring harness and connector
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 line (Refer to GROUP 54C -
Troubleshooting ).
STEP 2. Check whether the diagnosis code is reset.
Check again if the diagnosis code is set to the audio unit.
(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 audio unit.
The trouble can be an intermittent malfunction (Refer to GROUP 00 -
How
to use Troubleshooting/inspection Service Points -
How to Cope with Intermittent
Malfunction ).
Go to Step 2.
Repair the CAN bus line (Refer to GROUP 54C -
Troubleshooting 
).