Electrical Power Steering System (EPS)

DTC U0100 Engine time-out error
DTC U0121 ASC time-out error
DTC U0141 ETACS time-out error

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 CAN Bus Diagnostics Chart ).
- Whenever ECU is replaced, ensure that the CAN bus lines are normal.

OPERATION

The signals from the engine control module (ECM), ASC-ECU, and ETACS-ECU are sent to the EPS-ECU.

FUNCTION

The signals from the engine control module (ECM),ASC-ECU, and ETACS-ECU are sent to the EPS-ECU for motor control.

TROUBLE JUDGEMENT

Check Conditions

- The power supply circuit system DTC C1540, C1541 is not set.
- The DTC related to engine circuit system, ASC circuit system, and ETACS circuit system is set.

Judgement Criterion

The signals from the engine control module (ECM), ASC-ECU, and ETACS-ECU are not sent, and the microcomputer determines that there is a problem in the system.

Fail Safe, Back Up Function

- The EPS-ECU illuminates the electric power steering warning display, and sets the DTCs U0100, U0121, and U0141. However, the assist operation is limited only with the DTC U0121.

PROBABLE CAUSES

- Malfunction of CAN bus line
- Malfunction of the EPS-ECU
- Malfunction of the engine control module (ECM)
- Malfunction of the ETACS-ECU
- Malfunction of the ASC-ECU

DIAGNOSIS

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

Use scan tool to diagnose the CAN bus lines.

Q. Is the check result normal?

YES Go to Step 3.
NO Repair the CAN bus lines CAN Bus Diagnostics Chart). 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.

Q. Is the DTCs U0100, U0121 or U0141 set?

YES Go to Step 3.
NO This diagnosis is complete.
STEP 3. Using scan tool MB991958, check the DTC

Use scan tool MB991958 to check if the same DTC (time-out) is set in the other ECU (CAN-C).

Q. Is any DTC set?

YES (DTC U0100 is set) : Replace the engine control module (ECM), and then go to Step 4.
YES (DTC U0121 is set) : Replace the ASC-ECU, and then go to Step 4.
YES (DTC U0141 is set) : Replace the ETACS-ECU, and then go to Step 4.
NO (No DTC is set.) : Go to Step 4.
STEP 4. Check whether the DTC is reset

(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.

Q. Is the DTCs U0100, U0121 or U0141 set?

YES Replace the EPS-ECU (Refer to Service and Repair ). Then go to Step 5.
NO Intermittent malfunction How to Cope With Intermittent Malfunctions).
STEP 5. Check whether the DTC is reset

(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.

Q. Is the DTCs U0100, U0121 or U0141 set?

YES Return to Step 1.
NO This diagnosis is complete.