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

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 san 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?

Go to Step 2.

Repair the CAN bus line. Refer to GROUP 54C, Can bus Diagnostics Table

. 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?

	Replace the ECM. When the ECM is replaced, register the ID code. Refer to GROUP 42B, ID Code Registration Necessity Judgment Table <Vehicles with KOS> or GROUP 42C, ID Codes Registration Judgment Table <Vehicles with WCM> . Then go to Step 3.

	It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - 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?

	Replay the troubleshooting.

	The inspection is complete.