Mechanics

Wheel Speed Sensor Replacement

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How to Replace an ABS Wheel Speed Sensor

The ABS brake system of your car depends on a variety sensors and electronic devices to control and activate the system. None is more important than the ABS wheel speed sensor. These sensors which are located on all fours wheels or on the two front wheels and one sensor in the rear differential monitoring the rotation speed of each rear wheel. This is performed to allow the main ABS controller to differentiate the brake system pressure while the brake system is being applied. By doing this the wheel that is rotating a lesser a mount than the remaining wheels will experience a brake fluid drop in pressure to allow the wheel to rotate at the same rate as the remaining wheels. 

An ABS wheel sensor is one of the most prone failures in an ABS brake system. If an ABS wheel sensor has failed it will usually illuminate the red or yellow brake system warning light. To determine if a wheel speed sensor has failed there is one of two methods this can be achieved. First and most straight forward process is to attach a ABS system scan tool and retrieve the trouble codes. Once the code is discovered finding the code definition is next. This trouble code will help determine which sensor has failed. The more cumbersome method is to remove the electrical connector from each wheel sensor. Using a multi-meter test the ohms reading through the sensor to find the sensor that is either shorted or out of operating range. 

An additional test would be to set the multi-meter to the voltage setting and rotate the wheel and record the voltage for each wheel. While the wheel is rotating the meter should read a small amount of voltage depending on the speed of the wheel's rotation. Once the malfunctioning sensor has been located follow the steps below to remove and replace the sensor.

You will need the following tools and diagnostic equipment to perform this task:

1. Basic wrench and socket set.

2. A multi meter or abs scan tool

3. Protective gloves, clothing and eyewear.

4. Replacement ABS wheel speed sensor

5. Car jack with jack stands
 

Before you begin place your car on level ground with the emergency brake on (unless checking the rear ABS sensor, in this case block the front wheels from rolling)

Step 1 - First, you must locate the malfunctioning wheel sensor. This is done by using a scan tool or multi-meter. Plug in an ABS scan tool and follow the prompts to retrieve the trouble code associated with a failed wheel speed sensor.

Step 2 - If a scan tool is not available you can use a voltage multi meter. Disconnect the wiring connector at each wheel. Next attach the meter leads to each of the ABS connector terminals that lead to the wheel sensor being tested.

Step 3 - Once the failed wheel sensor has being discovered remove the sensor mounting bolts, or remove the tire and bearing hub. (Some ABS wheel sensors are intergraded into the wheel bearing hub)

Step 4 - Next, Inspect the sensor stator ring to confirm that there is no damage existing to the ring. If the ring shows signs or damage replacement is required.

Step 5 - Then, reinstall the new sensor or wheel bearing hub and reassemble.

Step 6 - Reconnect the electrical connector.
 

Once the new sensor is installed the system should run tests confirming is operating normally. At this point the warning light will go out. Some systems might require a ABS scan tool to reset the system, but this not typical. If further assistance is needed, our certified car repair technicians are ready to answer your car questions.
 

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AUTHOR


Written by
Co-Founder and CEO of 2CarPros.com
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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Article first published (Updated 2013-11-14)