Code No.C1200: Front right wheel speed sensor (open circuit/short to earth/short to power supply)




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/Active stability control system-ECU. The ABS/Active stability control system-ECU uses the frequency of the pulse signals to determine the wheel speed.

DIAGNOSIS CODE SET CONDITIONS


The ABS/Active stability control system-ECU detects an open circuit, short to earth or short to power supply by monitoring the voltage fluctuation in the front right wheel speed sensor circuit. It also detects short between the terminals of the front right wheel speed sensor and short to other wheel speed sensors.

PROBABLE CAUSES



DIAGNOSIS PROCEDURE

STEP 1. Connector check: A-02 front right wheel speed sensor connector

Q. Is the check result normal?

Go to Step 2.

Repair the defective connector.

STEP 2. Remove the front right wheel speed sensor and check it.
Refer to .

Q. Is the check result normal?
Go to Step 3.
Replace the front right wheel speed sensor (Refer to ).

STEP 3. Connector check: A-06 ABS/Active stability control system-ECU connector

Q. Is the check result normal?

Go to Step 4.

Repair the defective connector.

STEP 4. Resistance and voltage measurement at the A-06 ABS/Active stability control system-ECU connector.


(1)Disconnect the A-02 front right wheel speed sensor Connector and A-06 ABS/Active stability control system-ECU connector, and connect special tool ABS Check Harness (MB991984) to the wiring harness-side connector.
note Do not connect special tool ABS Check Harness (MB991984) to the ABS/Active stability control system-ECU.

(2)Resistance between special tool ABS Check Harness (MB991984) connector terminal No.28 and body earth
OK: Open circuit or more than 1 kΩ
(3)Turn the ignition switch to the "ON" position.

(4)Voltage between special tool ABS Check Harness (MB991984) connector terminal No.28 and body earth
OK: 0 V
(5)Turn the ignition switch to the "OFF" position.

(6)Resistance between special tool ABS Check Harness (MB991984) connector terminal No.29 and body earth
OK: Open circuit or more than 1 kΩ

Q. Are the check result normal?

Go to Step 5.

Repair the wiring harness between A-06 ABS/Active stability control system-ECU connector terminal Nos. 28 or 29 and A-02 front right wheel speed sensor connector terminal No.1 or 2.

STEP 5. Resistance measurement at A-06 ABS/Active stability control system-ECU and A-02 front right wheel speed sensor connector.


(1)Disconnect the A-02 front right wheel speed sensor Connector and A-06 ABS/Active stability control system-ECU connector, and connect special tool ABS Check Harness (MB991984) to the wiring harness-side connector.
note Do not connect special tool ABS Check Harness (MB991984) to the ABS/Active stability control system-ECU.

(2)Resistance between special tool ABS Check Harness (MB991984) connector terminal 28 and A-02 front right wheel speed Sensor Connector terminal 1
OK: 10 Ω or less

(3)Resistance between special tool ABS Check Harness (MB991984) connector terminal 29 and A-02 front right wheel speed sensor connector terminal 2
OK: 10 Ω or less

Q. Is the check result normal?

Go to Step 6.

Repair the wiring harness between A-06 ABS/Active stability control system-ECU connector terminal Nos. 28 or 29 and A-02 front right wheel speed sensor connector terminal No.1 or 2.

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.C1200 set?

Replace the hydraulic unit (integrated with ABS/Active stability control system-ECU). Then perform the variant coding and write the VIN data (Refer to GROUP 00, Precautions Before Service - How to Perform Variant Coding ).

The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).