Hands-Free Cellular Phone System

DTC U0019: Bus Off (CAN-B)

CAUTION:
- If DTC U0019 is set, be sure to diagnose the CAN bus line.
- When replacing the ECU, always check that the communication circuit is normal.

TROUBLE JUDGMENT
When the hands free module is returned from the bus off state, or when the bus error is indicated to the hands free module state, the DTC U0019 (CAN-B) is set.

COMMENTS ON TROUBLE SYMPTOM
The hands free module, power supply for the hands free module, ground circuit, or CAN bus line may have a problem.

PROBABLE CAUSES
- The hands free module may be defective.
- The CAN bus line may be defective.

DIAGNOSIS

Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: Vehicles Communication Interface (V.C.I.)
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)

STEP 1. Using scan tool MB991958, diagnose the CAN bus line.

Use scan tool MB991958 to diagnose the CAN bus lines.

CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.





1. Connect scan tool MB991958. Refer to "How to connect the Scan Tool (M.U.T.-III)." Scan Tool Connecting
2. Turn the ignition switch to "ON" position.
3. Diagnose the CAN bus line.

Q : Is the check result normal?

YES : Go to Step 2.

NO : Repair the CAN bus line. (Refer to Controller Area Network, Diagnosis.) On completion, go to Step 2.

STEP 2. Recheck for diagnostic trouble code.

Check again if the DTC is set to the hands free module.

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

Q : Is the DTC set?

YES : Replace the hands free module.

NO : The trouble can be an intermittent malfunction (Refer to General (Body and Chassis) -How to use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction).