Code No.C1206: Front left wheel speed sensor

OPERATION

The wheel speed sensor is a pulse generator. It consists of encoder (a plate on which north and south pole sides of the magnets are arranged alternately) for detecting wheel speed which rotates at the same speed as the road wheels. This sensor outputs frequency pulse signals in proportion to wheel speed.
The pulse signals, which the wheel speed sensor creates, are sent to the ABS-ECU. The ABS-ECU uses the frequency of the pulse signals to determine the wheel speed.

DIAGNOSIS CODE SET CONDITIONS

The ABS-ECU monitors the signals from the wheel speed sensors during driving. If the ECU detects malfunctions below, it sets the diagnosis code.

Missing of wheel speed sensor signals
When an abnormal wheel speed sensor signal is received
When one of the wheel speed sensor signals (from the front, rear, right and left wheels) is significantly different from the others

PROBABLE CAUSES

Improperly installed wheel speed sensor
Presence of dirt or other foreign particles on the encoder of the wheel speed sensor
Deformed encoder of the wheel speed sensor
Excessive gap between the wheel speed sensor and its encoder
Damaged wiring harness or connector
Malfunction of the wheel speed sensor
Malfunction of the hydraulic unit (integrated with ABS-ECU)

DIAGNOSIS PROCEDURE

STEP 1. Connector check: A-12 front left wheel speed sensor connector

Q. Is the check result normal?

Go to Step 2.

Repair the defective connector.

STEP 2. Check the installation condition of the front right wheel speed sensor.

Check that the front right wheel speed sensor is installed correctly.

Q. Is the check result normal?

	Go to Step 3.

	Correct the installation condition.

STEP 3. Remove the front left wheel speed sensor and check it.

Refer to

Q. Is the check result normal?

	Go to Step 4.

	Replace the front left wheel speed sensor (Refer to ).

STEP 4. Check the wheel bearing for excessive play.

Front: refer to GROUP 26, On-vehicle Service - Wheel Bearing Axial Play Check

Rear: refer to GROUP 27, On-vehicle Service - Wheel Bearing Axial Play Check

Q. Is the check result normal?

	Go to Step 5.

	Replace the hub assembly <Refer to GROUP 26, Front Axle Hub Assembly (Front) or GROUP 27, Rear Axle Hub (Rear)>.

STEP 5. Check the encoder for detecting wheel speed.

Check the encoder for presence of foreign objects or deformation.

Q. Is the check result normal?

	Go to Step 6.

	If foreign objects are found, clean the encoder. If deformation is found, replace the hub <Refer to GROUP 26, Front Axle Hub Assembly (Front) or GROUP 27, Rear Axle Hub (Rear)>.

STEP 6. Check whether the diagnosis code is reset.

caution

Before connecting or disconnecting the M.U.T.-III, turn the ignition switch to the "LOCK" (OFF) position.

Check again if the diagnosis code is set.
(1)Turn the ignition switch to the "ON" position.
(2)Erase the diagnosis code.
(3)Turn the ignition switch to the "LOCK" (OFF) position.
(4)Turn the ignition switch to the "ON" position.
(5)Check if the diagnosis code is set.
(6)Turn the ignition switch to the "LOCK" (OFF) position.
(7)Disconnect M.U.T.-III.

Q. Is code No.C1206 set?

Replace the hydraulic unit (integrated with ABS-ECU) (Refer to

The malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction