Multiport Fuel Injection (MFI)

DTC U0001: Bus Off

CAUTION:

- If the ECM output the DTC U0001, make sure to diagnose the CAN bus line.
- Before replacing the ECU, make sure that the communication circuit is operating normally.

DTC SET CONDITIONS

Check Conditions

- Always
Judgement Criteria

- Bus off error detected

FAIL-SAFE AND BACKUP FUNCTION

- None

TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)

- CAN line harness damage or connector damage.
- ECM failed.


DIAGNOSIS

Required Special Tools:

- MB991958: Scan tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991910: Main Harness A

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





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 to the data link connector.
(2)Turn the ignition switch to the "ON" position.
(3)Diagnose CAN bus line.
(4)Turn the ignition switch the "LOCK" (OFF) position.

Q. Is the CAN bus line normal?

YES Go to Step 2.

NO Repair the CAN bus line. CAN Bus Diagnostics Chart.
Then go to Step 3.

STEP 2. Recheck for diagnostic trouble code.

Check again if the DTC is set.

(1)Erase the DTC.

(2)Turn the ignition switch to the "ON" position.

(3)Check if the DTC is set.

(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is DTC U0001 set?

YES Replace the ECM. When the ECM is replaced, register the ID code. ID Code Registration Judgment Table or ID Codes Registration Judgment Table [Vehicles with WCM] Wireless Control Module (WCM).
Then go to Step 3.
NO It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions.
STEP 3. Recheck for diagnostic trouble code.

Check again if the DTC is set.

(1)Erase the DTC.

(2)Turn the ignition switch to the "ON" position.

(3)Check if DTC is set.

(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is DTC U0001 set?

YES Replay the troubleshooting.
NO The inspection is complete.