text.skipToContent text.skipToNavigation


Modern cars and trucks use a variety of sensors to send data from their components to their computers. These sensors regulate everything from your speedometer readout to the way your anti-lock braking system (ABS) functions.



What is a Wheel Speed Sensor?

Wheel speed sensors are often called ABS sensors. You’ll find them mounted on the axles of all ABS equipped vehicles. Look for this sensor on your wheel hubs, near the brake rotors.

You’ll find the rear wheel speed sensor mounted on the rear axle housing or wheel cylinder. The ABS sensor is a vital part of the braking system. Without a working ABS wheel speed sensor, the ABS system will fail to work properly.

How does a Wheel Speed Sensor Work?

The wheel speed sensor “sees” when your brakes are locked up. When your wheels are locked up, your tires fail to produce sufficient friction to stop you and your vehicle. When the sensor sees your brakes are locked up, it sends a signal to your vehicle’s ABS module. The ABS module then releases a small amount of brake pressure, which allows your tires to maintain friction against the road surface.

When activated, the ABS module sends many high frequency pulses to the brakes. These pulses originate at the speed sensor. ABS systems work well because there’s far more friction available to stop the vehicle when the wheels are rolling rather than sliding and skidding helplessly across the road’s surface.

How are Wheel Speed Sensors Made?

Most wheel speed sensors are made of a mix of plastic, aluminum, steel, and various electrical parts. The electrical parts are designed to work with the vehicle’s computer. Wheel speed sensors are often interchangeable, and many manufacturers use the same parts for different makes and models.

Why do Wheel Speed Sensors Fail?

  • Like many electrical parts, wheel speed sensors are sensitive to moisture, oxidation, heat, and other wear and tear encountered during normal driving conditions.
  • Improper installation and electrical connector maintenance may also cause your wheel speed sensors to fail.

What are the Symptoms of Failure?

  • Your ABS fails to modulate the brakes after your tires lose traction. You are most likely to notice this symptom on wet, slick, or icy road surfaces, exactly when you need it the most.
  • Your vehicle’s check engine light or ABS light may come on and stay on.

What are the Implications of Failure?

  • Although your brakes will continue to function properly after wheel speed sensor failure, the lack of ABS makes the vehicle far more difficult to stop in wet, slick, or icy conditions.
  • You may cause a traffic accident if your ABS malfunctions during a panic stop, even on dry surfaces.

Your vehicle’s wheel speed sensors are an important part of its braking system. Your brakes will functional normally without ABS, but it will become much more difficult to stop your vehicle in an emergency.

If you have questions or concerns about wheel speed sensors or any of your vehicle’s components, come into your local Pep Boys where we can answer any question, help you find any part, or perform any vehicle service you might need.