MMCS

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. (Check that the voltage is 10 V or more.)

DIAGNOSTIC FUNCTION
If the CAN-B circuit malfunction occurs, the CAN box unit sets DTC U0019.

JUDGMENT CRITERIA
With the ignition switch at the ON position and the system voltage at 10 -16 volts (data from ETACS-ECU), if the CAN box unit becomes unable to transmit data normally due to the CAN-B bus circuit malfunction, the CAN box unit determines that a problem has occurred.

TROUBLESHOOTING HINTS
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. Recheck for diagnostic trouble code.

Check again if the DTC is set to the CAN box unit.






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

Q : Is the DTC set?

YES : Go to Step 2.

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).

STEP 2. Using scan tool MB991958, diagnose the CAN bus line.

1. Turn the ignition switch to the "ON" position.
2. Diagnose the CAN bus line.
3. Turn the ignition switch to the "LOCK" (OFF) position.

Q : Is the CAN bus line found to be normal?

YES : 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).

NO : Repair the CAN bus line (Refer to Controller Area Network, Diagnosis).