What Happens When a Wheel Speed Sensor Goes Bad?(5 Symptoms)

A failing speed sensor impacts driving in a couple of ways. Notably, it has a direct impact on an automatic transmission. Since it relays critical wheel rotation speed to the control module, it prevents the wheels from locking up.

When the wheel speed sensor malfunctions, it causes dangerous situations. So, learning lousy wheel speed sensor symptoms will help you take the necessary steps.

Read more to know what to do!

What Is A Wheel Speed Sensor? What Does It Do?

Wheel speed sensors are part of your vehicle’s anti-braking system (ABS).

Wheel speed sensors are part of your vehicle’s anti-braking system (ABS). Their work is to monitor the speed of the front and rear wheels.

The ABS control module keeps you on the road (literally). This system picks information from the wheel’s sensors and makes sure that all the wheels are spinning at the right speed. If one wheel is out of sync, the ABS will correct it to match the other three wheels.

There are two types of wheel speed sensors: passive and active. 

Passive sensors were traditionally used to deliver analog signals to the ABS. On the other hand, active sensors record the signals using magnetic pulse sensors. 

Active sensors have more benefits than passive sensors in that they are more compact and resist electromagnetic interference. They also identify the direction of the wheels spinning and function through extreme temperature changes. 

What Happens When a Wheel Speed Sensor Goes Bad?

What Happens When a Wheel Speed Sensor Goes Bad

When a wheel speed sensor goes bad, it may cause Abs warning lights go on, Speedometer stop working, Anti-lock brakes stop working, Traction control and stability control stop working, or Pulsating brake pedal.

I will go into details below:

1. ABS Warning Lights Go On 

The first indicator that you’re having a problem with a wheel sensor is an illuminating ABS warning light. As I’ve indicated, wheel sensors are part of the ABS. The light will come up since the vehicle’s control module is not receiving information about how fast the wheels are spinning.

The ABS warning light could also mean that the sensor is disconnected, filled with debris, or worn out.

Nevertheless, the ABS light may illuminate because of other problems such as damaged brake pads, a faulty ABS pump, or a low brake fluid level.

2. Speedometer Stops Working

Speedometer Stops Working
Credit: https://wheelzine.com/

A faulty speed sensor can cause the speedometer to stop working, especially in older vehicles. You’ll notice that it stays at 0MPH, so get the vehicle checked out since you’re most likely to go over the speed limit without knowing.

3. Anti-Lock Brakes Stop Working

Inoperable anti-lock brakes are a safety concern. Unfortunately, when the wheel speed sensor goes bad, they are the first to go. This situation will also trigger the ABS light because the vehicle’s control module cannot tell whether the wheels are locking up. So, the system shuts them down.

When anti-lock brakes are not working, there’s a high chance that the wheels will lock when you hit the brakes, causing the vehicle to skid and lose control. So, I certainly hope that you get the car checked as soon as the ABS light comes up.

4. Traction Control and Stability Control Stop Working

Traction and stability control are safety features that should stay on. Traction control maintains traction between the wheels and the road in slippery conditions. It does this by limiting the spinning of the tires so that they stay connected to the road. Therefore, if traction is not working, your vehicle may skid or hydroplane dangerously on wet roads.

A traction control light is also likely to come up when a wheel speed sensor is not working.

5. Pulsating Brake Pedal

A bad wheel speed sensor means that one of the wheels is not spinning at the right speeds as the other three wheels. Hence, the ABS control module will signal that the tire is skidding, causing the traction system to kick in.

To this end, the variation in the wheel speeds will give you a feeling of pulsation or pumping when you brake.

Can You Drive with A Bad Wheel Speed Sensor?

No. You shouldn’t drive with a bad wheel sensor since it affects the anti-lock braking system and traction system are essential for driving safety. 

The vehicle’s control unit cannot determine the wheel’s speeding speed with a faulty wheel sensor. As such, it’s likely to increase the engine power or apply brakes at a higher rate than it should. This may cause locking the wheels or skidding, leading to a dangerous situation. 

For example, if you’re driving in the rain, the traction system failure can result in the vehicle hydroplaning and veering it off the road, resulting in a car accident. 

What Causes Wheel Speed Sensor Failure?

Various things can cause an ABS sensor to malfunction. Nonetheless, the most common are internal sensor failure or damage to the sensor tip. Use an ohmmeter to test the wheel speed sensor winding, then compare it to service specs.

Once you confirm that the sensor’s wiring is bad, replacing it will solve the issue and allow you to clear the ABS light.

Other causes of wheel speed sensor failure such as:

  • Debris Accumulation: When dirt accumulates on the speed sensor, it blocks its ability to relay a signal. 
  • Mismatched Tires: If you install different tires, they will rotate at different speeds causing the sensors to send wrong or mixed signals. 
  • High Heat: Since the wheel sensors mount near the braking system, they can malfunction because of the heat coming from the brakes.

Do You Need A Speed Sensor Replacement?

In some cases, you do not need to replace the sensor. For example, you can clean out debris, and the sensor will go back to functioning normally. Yet, if the sensor is not working correctly, it will need proper diagnosis and replacement. 

Wheel Speed Sensor Replacement Cost

The average wheel speed sensor replacement cost is around $225 to $265 for the parts. Labor is usually from $80 to $100, depending on your location. The procedure for replacing a speed sensor is around 45 minutes to an hour. 

Wheel Speed Sensor Location

Front-wheel speed sensors are near the brake rotors. But in the rear tires, you will find them in the rear-end housing of the rear tires. This location is for a car with four sensors. 

There will be a speed sensor on each of the front wheels in a vehicle with three sensors, but the rear wheel speed sensor will be on the rear axle. A car’s ABS typically dictates the number and location of sensors. 

These are the basic types of wheel speed sensor systems:

  • Four Sensor ABS: One sensor on each wheel 
  • Four Sensors, Two Channel ABS: There’s one sensor on each wheel, one channel at the front, and another for the rear. 
  • Three Sensor ABS, Three Channel ABS: This system has one sensor for each front wheel and one on the rear axle for the rear wheels. The front wheels are monitored separately from the rear wheels. 
  • Four Sensor, Three Channel ABS: Each wheel has one sensor, but the rear wheels are monitored on one controller. 

Can Wheel Speed Sensors Affect Transmission?

Yes. The ABS sensors not sending the correct information to the car’s computer will trickle into the Engine’s Control Unit (ECU). Since the ECU controls various driving components, it causes several issues.

If the transmission gets the wrong speed values, it cannot get the car into the correct gear. You may also notice that the transmission can lock up in first gear, or the gears shift with strong jerks.

Will A Wheel Speed Sensor Throw A Code?

Yes. A bad wheel speed sensor will throw a fault code. There are around 40 ABS codes, and half of them surround a malfunctioning wheel sensor. You will find numerous diagnostic procedures, but the easiest is using a diagnostic scanner that can read the ABS. After which, you will get the specific code then you can go ahead and find out its definition before undertaking repair or replacement procedures. 

You can buy basic diagnostic scanners below. They are must-have items for car owners

Autel OBD2 Scanner

Autel OBD2 Scanner Autolink AL319 Code Reader

ANCEL AD310 Classic Enhanced Universal OBD II Scanner

ANCEL AD310 Classic Enhanced Universal OBD II Scanner

Sum up

Now you know what happens when a speed sensor goes bad. Apart from the ABS light illuminating, it can bring safety issues, especially when driving in inclement weather. Next time you see any signs of a bad speed sensor, please have it diagnosed and repaired. 

See also:

Broken CV Axle – Important Things You Need To Know

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