The ABS wheel speed sensor has multiple functions, making it a vital part of your automobile. When one begins to fail, you might notice several symptoms.
This article reviews the top for symptoms of a bad ABS wheel speed sensor, its location, function, and replacement cost. Let’s take a quick look at what signs you can expect.
The most common symptom of a bad ABS sensor is an ABS warning light showing up on your dashboard. You may also notice issues like a pulsating brake pedal while braking or a complete loss of the anti-lock brake system.
As you can see, there are actually not that many ways to tell if an ABS sensor has gone bad. This is mainly because the ABS control module will light up the ABS warning light and deactivate the system to prevent accidents. Here is a more detailed list of the most common symptoms of a bad ABS wheel speed sensor.
Bad ABS Wheel Speed Sensor Symptoms
1. Illuminated Warning Lights
Your dashboard contains a variety of important lights that alert you to danger. When the ABS wheel speed sensor fails, the ABS light is probably one of the first sign your will notice of all bad ABS wheel speed sensor symptoms.
At first, it might simply cause the ABS warning light to come on. However, when the other systems stop functioning properly, you might also see the traction and stability control warning lights.
In rare cases, defective ABS wheel speed sensors can cause the speedometer to stop registering.
2. Pulsating Brake Pedal while braking
The ABS sensors measure the speeds of each wheel, and if one of the ABS sensors has gone bad, it will read the wrong speed on one or more wheels. This will cause the ABS control module to get tricked and thinking the car is sliding on a slippery surface.
This will cause the ABS and traction control to kick in, and you will feel it by feeling a pulsating or pumping brake pedal while braking.
3. Loss of Anti-lock Brakes
When an ABS wheel sensor fails, it causes the anti-lock brakes to be inoperable. Anytime a fault is noticed, the system triggers an alert, and the ABS warning light comes on.
From here, the vehicle’s electronic control module stops receiving valuable data from the sensor. The computer relies on this information to determine if the wheels are locking up and require support.
Because the system doesn’t know what is happening, the ABS shuts down until the repair is made.
4. Loss of Traction or Stability Control
Not only can you lose anti-lock brakes, but also other functions, such as stability control, traction control, roll stability, and hill-start assist. When the sensor stops sending information, the computer shuts down these systems as well.
However, you can experience problems even when the ABS light isn’t on. If you struggle to maintain traction in poor weather conditions or notice handling issues when you brake quickly, the ABS wheel speed sensor might be to blame.
It could also be caused by damaged wiring connections running from the sensor to the ECM.
ABS Wheel Speed Sensor Location
The ABS wheel speed sensor is located at the wheel, behind the brake rotor, but some are placed directly on the axle. Each vehicle contains a varying amount of ABS wheel speed sensors.
If the system contains four ABS wheel speed sensors, there will be one at each wheel behind the rotor. Systems with three sensors have two at each front wheel and another on the rear axle instead of at the wheel.
The ABS type determines how many sensors the vehicle contains. Here are four ABS configurations.
Two-channel, four-sensor ABS: One sensor is located on each wheel, but there’s a channel in the front and one for the rear. When any speed sensors detect a wheel lockup, ABS engages at that part of the vehicle.
Three-channel, three-sensor ABS: There is one sensor located at each front wheel and one located on the rear axle. While the rear wheels are monitored at the same time, the front wheels are evaluated separately.
Three-channel, four-sensor ABS: While there are sensors located at every wheel, the rear wheels run on one controller.
Four-sensor ABS: One sensor is located at each wheel and monitored separately. This is the most common configuration with modern vehicles.
ABS Wheel Speed Sensor Function
The ABS wheel speed sensor can also be called an ABS brake sensor or, more plainly, an ABS sensor. Whatever it is called, it is a critical part of the ABS.
The anti-lock braking system (ABS) is found on most new vehicles. ABS wheel sensors are attached to wheels or the axle to measure the rotation speed of the wheels. Most ABS sensors contain a toothed ring and magnet that’s enclosed with a coil. Contact between the magnet and ring creates an electric field, which turns into the signal that is sent to the ABS controller.
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From here, the controller determines the speed of each wheel or axle. This information is then transmitted to the Engine Control Module (ECM).
When the ECM sees that a wheel is locking up, the ABS is activated. It operates at such a fast speed that it often creates a grinding noise with a pulsating sensation.
If the vehicle is also equipped with traction control, the ABS sensor helps control the movement of the vehicle in precarious situations. When traction is lost, the speed of one wheel will be different than the others, causing the system to kick in.
The computer reduces the amount of braking force being applied to the wheel, causing trouble. When this force decreases, it allows the wheel to regain grip and rotate normally again. These same sensors run the stability control systems in modern cars as well.
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ABS Wheel Speed Sensor Replacement Cost
The average ABS wheel speed sensor replacement cost is between $200 and $400 per sensor, depending on the car model and labor costs. You can expect to pay about $100 to $150 for the wheel speed sensor and another $100 to $300 for the labor.
ABS wheel speed sensors on luxury vehicles can often cost more, plus some models can be harder to work on, which increases the labor cost.
However, it’s not difficult to replace the ABS wheel speed sensor yourself with a few tools. If you have basic mechanical knowledge, this might be a project worth tackling in your home garage. They can become stuck after a while though, so you may need some heat source to remove them.