Electrical Power Steering System (EPS)

DTC U0100 Engine timeout error
DTC U0121 ABS timeout error
DTC U0141 ETACS timeout 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 Scan Tool Testing and Procedures).

- Whenever ECU is replaced, ensure that the CAN bus lines are normal.

OPERATION

- The signals from the engine control module (ECM), ABS-ECU [vehicles with ABS], ASC-ECU [vehicles with ASC], and ETACS-ECU are sent to the electric power steering-ECU.

FUNCTION

- The signals from the engine control module (ECM), ABS-ECU [vehicles with ABS], ASC-ECU [vehicles with ASC], and ETACS-ECU are sent to the electric power steering-ECU for motor control.

TROUBLE JUDGMENT

Check Conditions

- The power supply circuit system DTC C1540, C1541 is not set.

- The DTC related to engine circuit system, ABS circuit system [vehicles with ABS], ASC circuit system [vehicles with ASC], and ETACS circuit system is set.

Judgment Criterion

- The signal from the engine control module (ECM) is not received for 55 seconds.

- The signal from the ABS-ECU [vehicles with ABS], ASC-ECU [vehicles with ASC], and engine control module (ECM) cannot be received for 11 seconds.

- The signals from the engine control module (ECM), ABS-ECU [vehicles with ABS], ASC-ECU [vehicles with ASC], and ETACS-ECU are not sent, 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 display, and sets the DTC 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 electric power steering-ECU

- Malfunction of the engine control module (ECM)

- Malfunction of the ETACS-ECU

- Malfunction of the ABS-ECU [vehicles with ABS]

- Malfunction of the ASC-ECU [vehicles with ASC]

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 (Vehicles with CAN communication system)

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 DTC 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 (timeout) is set in the other ECU (CAN-C).

Q. Is any DTC set?

YES (Code No. U0100 is set) : Replace the engine ECU, and then go to Step 4.
YES (Code No. U0121 is set) : Replace the hydraulic unit (integrated with ABS-ECU) [vehicles with ABS], hydraulic unit (integrated with ASC-ECU) [vehicles with ASC], and then go to Step 4.
YES (Code No. 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 DTC U0100, U0121 or U0141 set?

YES Replace the electric power steering-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 DTC U0100, U0121 or U0141 set?

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