37-U1073 BUS OFF

DTC U1073 Bus-off

caution

If there is any problem in the CAN bus lines, an incorrect DTC may be set. Prior to this diagnosis, diagnose the CAN bus lines (Refer to GROUP 54C, CAN Bus Diagnostics Table ).
Whenever ECU is replaced, ensure that the CAN bus lines are normal.

OPERATION

FUNCTION

The signals from the ECUs communicate with the electric power steering-ECU for motor control.

TROUBLE JUDGMENT

Check Conditions

Judgment Criterion

The signals from the ECUs cannot communicate (bus off), and the microcomputer determines that there is a problem in the system.

Fail Safe, Back Up Function

The electric power steering-ECU illuminates the electric power steering warning symbol to limit the power assistance, and sets DTC No. U1073.

PROBABLE CAUSES

DIAGNOSIS

STEP 1. Using scan tool MB991958, diagnose the CAN bus diagnostics

Use scan tool to diagnose the CAN bus lines.

Is the check result normal?

Go to Step 3

Repair the CAN bus lines (Refer to GROUP 54C - Diagnosis/CAN Bus Diagnostics Table

). On completion, go to Step 2

STEP 2. DTC recheck after resetting CAN bus lines

(1) Erase the DTC.

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

(3) Check if the DTC is set.

Is DTC U1073 set?

Go to Step 3

This diagnosis is complete.

STEP 3. Check whether the DTC is set again.

(1) Erase the DTC.

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

(3) Check if the DTC is set.

Is DTC U1073 set?

Replace the electric power steering-ECU (Refer to

).Then go to Step 4

Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/How to Cope with Intermittent Malfunctions

STEP 4. Check whether the DTC is set again.

(1) Erase the DTC.

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

(3) Check if the DTC is set.

Is DTC U1073 set?

Return to Step 1

This diagnosis is complete.