An ABS wheel speed sensor counts wheel revolutions. It reads the wheel rotation and measures it in revolutions per minute (RPMs). It should not be confused with the gauge on the dashboard that displays the engine RPM via the tachometer.
Common causes that trigger an ABS warning or light to come on are:
In a system with four sensors, a sensor can be found at each wheel near the rotor. In a system with three sensors, in addition to a sensor located at each front wheel, the third sensor for the rear is located in the rear axle, typically.
The type of ABS system a vehicle has will indicate how many sensors are on the vehicle. Older passenger cars will have alternative systems, but these listed below are the four basic types.
To diagnose ABS problem you will need an OBD-II scanner that can read codes from the ABS module of your vehicle. Below are a few examples of multi-system OBD II scanners that can diagnose ABS faults on many makes and models:
It is important to check all speed sensors for functionality as it is possible only one sensor may need replacing. Also, it is possible that the sensor may not need to be replaced at all and cleaning the sensor is all that is needed. If the ABS or stability control lights remain on after cleaning the sensor comprehensive diagnostics should be conducted.
Keep in mind that road debris, dirt, and grease at the tip of the ABS sensor can prevent the ABS system from operating properly. If this is the case, you can typically clean the sensor and reinstall it instead of replacing it.
Secondly, wheel speed sensors can be accidentally and unknowingly damaged in other ways, especially if other automotive repair work has been done in the wheel area, such as brake work. If this is the case, the vehicle should be brought back to the repair shop that performed the repairs to be inspected for damage.
A common problem with a malfunctioning wheel speed sensor is with the wiring harness that is connected to the sensor, which transmits the speed data to the ABS control unit. First, visually inspect the ABS sensor harness.
Replacing a wheel ABS sensor on most vehicles is a very easy procedure that most DIYers can complete in about 30 to 60 minutes. Watch the video below for an example on how to change a wheel ABS sensor on a car.
Depending on where the customer resides and what kind of vehicle they drive, a wheel speed sensor replacement can cost anywhere from under $200 to between $300-400, including parts and labor.
Labor rates will vary among repair shops, and the cost of replacing the speed sensor or any additional wiring will depend on the type of vehicle.
Car owners will save between $100-150 replacing the part themselves, although there work involved and some portions of the repair require special tools, which could factor into the cost as well if someone were to repair it at home.