TCL/ASC-ECU

DTC U1073: Bus off

DIAGNOSIS

CAUTION:

- If DTC U1073 is set in the TCL/ASC-ECU, always diagnose the CAN main bus line. If there is any fault in the CAN bus lines, an incorrect DTC may be set.
- Whenever the ECU is replaced, ensure that the communication circuit is normal.

TROUBLE JUDGMENT

This code is stored when the TCL/ASC-ECU has ceased the CAN communication error (bus off). Then, if a penalty mode is entered after approximately five minutes, regular data transmission 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 TCL/ASC-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 CAN Bus Diagnostics Chart). Then go to Step 3.

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 TCL/ASC - ECU). 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)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.