ABS

DTC U1073: Bus off

CAUTION:
^ If there is any problem in the CAN bus lines, an incorrect diagnostic trouble code may be set. Diagnose the CAN bus lines before the DTC.
^ Whenever the ECU is replaced, ensure that the CAN bus lines are normal.

TROUBLE JUDGMENT
This code is stored when the ABS-ECU has ceased the CAN communication (bus oft). Then, if a penalty mode is entered after approximately five minutes, the regular data transmission from the ABS-ECU will be cancelled.

TROUBLESHOOTING HINTS (The most likely causes for these DTCs are to set are:)
^ Damaged wiring harness or connector
^ Malfunction of the hydraulic unit (integrated with ABS-ECU)

DIAGNOSIS

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

STEP 1. Using scan tool MB991958, diagnose the 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 the CAN bus line.
4) Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the CAN bus line found to be normal?
YES: Go to Step 2.
NO: Repair the CAN bus line. Then go to Step 2.

STEP 2. Recheck for diagnostic trouble code. Check again if the DTC is set.





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

Q: Is DTC U1073 set?
YES: Replace the hydraulic unit (integrated with ABS-ECU). Then go to Step 3.
NO: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction.

STEP 3. Recheck for diagnostic trouble code. Check again if the DTC is set.





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

Q: Is DTC U1073 set?
YES: Go to Step 1.
NO: The procedure is complete.