How to Replace an ABS Wheel Speed Sensor

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 yellowbrake 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.

ABS Wheel Speed Sensor location

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 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.

ABS Wheel Speed Sensor back plate fixing