Code No. U0126: Steering Wheel Sensor Time-out <Vehicles with FCM-LS>

caution

If diagnosis code U0126 is set in the engine-ECU, surely perform CAN bus line diagnosis.
Replace ECU after certainly confirming that the communication circuits are normal.

TROUBLE JUDGEMENT

Check Conditions

After 2 seconds since the ignition switch is turned "ON" or since the completion of engine start.
Battery positive voltage is more than 10 V and is less than 16.5 V.

Judgement Criterion

Unable to receive steering wheel sensor signals through the CAN bus line for 4 seconds.

COMMENTS ON TROUBLE SYMPTOM

Current malfunction

The failure is possibly caused by malfunction of the harness and connector in CAN bus line between engine-ECU and steering wheel sensor, by malfunction in the power supply system of steering wheel sensor, in steering wheel sensor itself, in engine-ECU.

Past malfunction

Proceed with troubleshooting focusing on malfunction of the harness and connector in CAN bus line between engine-ECU and steering wheel sensor and malfunction in the power supply system of steering wheel sensor. For diagnosis procedure, refer to how to cope with past malfunctions. (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points, How to Treat Past Trouble).

note

In the case of past malfunctions, M.U.T.-III CAN bus line diagnosis cannot detect a malfunction even if there is a malfunction in CAN bus. Therefore, check CAN bus line as in the case of response to intermittent malfunctions. (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points, How to Cope with Intermittent Malfunctions). It is possible to narrow down areas with a high possibility of malfunctions from diagnosis codes set to each ECU that performs CAN communication (Refer to GROUP 54C - Explanation about the M.U.T.-III CAN Bus Diagnostics).

FAIL-SAFE AND BACKUP FUNCTION

The RMS and FCM-LS are prohibited.

PROBABLE CAUSES

Failed harness and connector
Failed steering wheel sensor
Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnosis.

Use M.U.T.-III to perform CAN bus line diagnosis.

Q. Is the check result normal?

	Go to Step 2.

	Repair CAN bus line (Refer to GROUP 54C - Troubleshooting - CAN Bus Diagnosis Table ). After repairing CAN bus line, go to Step 6 .

STEP 2. M.U.T.-III other system diagnosis code.

Check if the ASC-ECU set a diagnosis code related to the steering wheel sensor.

Q. Is diagnosis code set?

	Perform troubleshooting of the ASC system (Refer to GROUP 35C - Troubleshooting, Diagnosis Code Chart ).

	Go to Step 3.

STEP 3. M.U.T.-III other system diagnosis code.

Check that the other ECU performing CAN communication with steering wheel sensor sets diagnosis code No. U0126 (Refer to GROUP 54C - CAN-related Diagnosis Code Table

Q. Is diagnosis code set?

	Go to Step 4.

	Go to Step 5.

STEP 4. M.U.T.-III diagnosis code.

Confirm again whether the diagnosis code is set in the engine-ECU.

Erase the set diagnosis code.
Ignition switch: "LOCK" (OFF) → "ON"
Confirm whether the diagnosis code is set.

Q. Is diagnosis code set?

	After replacing steering wheel sensor (Refer to GROUP 35C - Steering Wheel Sensor), go to Step 6.

	Intermittent malfunction in CAN bus line between engine-ECU and ASC-ECU. (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points, How to Cope with Intermittent Malfunctions).

STEP 5. M.U.T.-III diagnosis code.

Confirm again whether the diagnosis code is set in the engine-ECU.

Erase the set diagnosis code.
Ignition switch: "LOCK" (OFF) → "ON"
Confirm whether the diagnosis code is set.

Q. Is diagnosis code set?

	After replacing engine-ECU, go to Step 6.

	Intermittent malfunction in CAN bus line between engine-ECU and ASC-ECU. (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points, How to Cope with Intermittent Malfunctions).

STEP 6. M.U.T.-III diagnosis code.

Confirm again whether the diagnosis code is set in the engine-ECU.

Erase the set diagnosis code.
Ignition switch: "LOCK" (OFF) → "ON"
Confirm whether the diagnosis code is set.

Q. Is diagnosis code set?

	Go to Step 1.

	This diagnosis is complete.