- A faulty wheel speed sensor can show symptoms like an illuminated anti-lock brakes (ABS) warning light, unresponsive ABS, failed traction and stability control, a pulsating brake pedal, and a broken speedometer.
- A wheel speed sensor is responsible for recording the speed of its respective wheel and sends the data to the ABS module.
- Wheel speed sensors break because they’re built into the bearing hub. If the bearing fails, the sensor will typically fail along with it due to noise and vibration.
The anti-lock brakes (ABS) and other vehicle dynamics systems constantly monitor the speed of all four wheels of a vehicle. Input is provided by specially designed sensors mounted very near a toothed wheel connected to the wheel hub or axle.
These vehicle dynamics systems make vehicles safer to drive, but they can only do what they’re designed to do if all their inputs are providing accurate information.
Faulty wheel speed sensors should be addressed immediately to ensure road safety. Here are some symptoms of bad wheel speed sensors to watch out for:
Faulty Wheel Speed Sensor Symptoms
It’s best to replace your wheel speed sensors as soon as they show signs of wear, so be on the lookout for these symptoms:
ABS Warning Light Comes On
Your ABS warning light is a small yellow or orange light on your dashboard. Along with other indicator lights in your vehicle, you’ll notice it flash briefly whenever you start your car. However, if the speed sensors in your ABS are faulty, they’ll most likely stay on until you replace your speed sensors.
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Without a functional ABS sensor, your ABS control module won’t receive any data about your vehicle’s wheel speed. This will force your entire anti-lock braking system to shut down, leaving your wheels at risk of locking. To restore your ABS, you’ll have to replace your broken wheel speed sensor with a new one. Note that your regular brakes will still work, you just won’t have ABS function.
Traction and Stability Control Failure
If your vehicle has traction and stability control, then these systems will also shut down when your ABS sensor malfunctions. Your wheel speed sensors send data to your traction and stability control, and if they stop transmitting this data, these features will stop working.
Traction control automatically applies pulsating brake pressure only to the spinning wheel (think wet grass or mud), which causes equal torque to be delivered to both traction wheels.
Pulsating Brake Pedal
Does the pedal feel like it’s pulsating when you hit the brakes?
On hard braking, brake pedal pulsation (the pedal “bouncing” under your foot) is normal, but as in the example of the 2001 Pontiac referenced above, incorrect application of the traction control system might make the brake pedal feel odd.
A bad ABS sensor will, however, typically illuminate the ABS light and shut the ABS system down completely if a wheel speed sensor has failed or the wiring is damaged, so you won’t typically feel pedal pulsation due to a bad ABS sensor.
A bad ABS sensor will, however, typically illuminate the ABS light and shut the ABS system down completely if a wheel speed sensor has failed or the wiring is damaged, so you won’t typically feel pedal pulsation due to a bad ABS sensor.–Richard McCuistian, ASE Certified Master Automobile Technician
While it doesn’t happen often, a broken ABS sensor can cause your speedometer to fail. This is only true, however, if the speed sensors provide vehicle speed information through the ABS to the PCM and instrument cluster.
What Is a Wheel Speed Sensor?
As you drive, a wheel speed sensor record the speed of its respective wheel’and sends the data to the ABS module. Four-wheel ABS always has a sensor for each wheel typically installed directly on the wheel axle or behind the wheel’s brake rotor.
What Does a Wheel Speed Sensor Do?
When in a hard braking situation, if the wheels lock, you lose your ability to steer the vehicle. Even though you’re turning the wheel, if the front wheels aren’t rolling, the car will keep going straight, which can lead to serious road accidents.
Furthermore, on a curve, wheel lockup will typically cause dangerous sideways skidding, and this is why rear anti-lock brakes became a requirement on pickups and vans in the 1980s.
If the ABS module detects any of the wheels slowing too rapidly during a hard braking maneuver, the hydraulic control unit will automatically use its isolation solenoids to block brake fluid pressure to any or all wheels that are beginning to slide, which helps keep you in control of the vehicle.
Other Wheel Speed Sensor FAQ
Since many wheel speed sensors are built into the bearing hub, if the bearing fails, the sensor will typically fail along with it due to noise and vibration.
Like other parts of your braking system, your ABS sensors can also wear out over time and simply stop working. Whatever the cause is, it’s best to replace your wheel speed sensors as soon as they fail.
While you can still drive your vehicle even if your wheel speed sensor isn’t working, it isn’t a good idea to do so. The ABS is an important safety feature in your vehicle, and it can’t function if your wheel speed sensors aren’t working.
You can still use your vehicle’s brakes, but they might lock up if you need to stop suddenly. This puts you at risk for traffic accidents, so it’s best not to delay your visit to the mechanic. Replacing the ABS sensors is relatively easy for them, and you can expect most mechanics to get the job done within an hour.
Most wheel speed sensors last around 30,000 to 50,000 miles but will usually last the life of the vehicle. However, this can change depending on several factors, like how you drive, how frequently you drive, and the condition of the roads you often travel on.
Wheel speed sensors can go for $10 to $680. However, the final price depends on several factors, including your vehicle’s make, model, and the product’s brand.
Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.