The wheel speed sensor is one of those parts that most people never consider until it goes bad. And when it does, all kinds of things can happen; I don’t mean that as a good thing. It can put you, passengers, and other road users in dangerous situations.
This article will dive into what happens when a wheel speed sensor goes bad, why it goes bad, and what you need to do to get your vehicle back in good working order. We also take a peek at replacement costs. So keep reading to learn everything you need to know!
Let’s get started.
What Is a Wheel Speed Sensor and What Is Its Function?
A wheel speed sensor, also known as an ABS (Anti-lock Braking System) sensor or Vehicle Speed Sensor (VSS), is a small electronic device located on each wheel hub or brake rotor. Its function is to monitor the speed of each wheel and send that information to the vehicle’s computer. The computer then uses this information to determine if a wheel is locking up or skidding and if so, the ABS system will intervene to prevent a loss of control.
The ABS works by rapidly pulsing the brake pressure to a wheel about to lock up. This allows the wheel to maintain traction and continue to rotate, thus preventing a skid. The ABS relies on the accurate and timely information provided by the wheel speed sensors to make these rapid pressure adjustments.
In addition to ABS, the information from the wheel speed sensors is also used by other systems in the vehicle, such as the traction control system (TCS) and the stability control system (SCS). These systems also use the information from the wheel speed sensors to determine if a wheel is slipping and, if so, will intervene to regain traction and stability.
What Happens When a Wheel Speed Sensor Goes Bad?
When a wheel speed sensor goes bad, it can cause a number of issues with your vehicle’s ABS and stability control. As mentioned, this sensor is responsible for sending signals to the ABS control module, indicating the speed of each wheel. If the sensor is faulty, the ABS module will not receive accurate information and may not function properly.
One of the most immediate effects is that the faulty sensor will send a signal to the vehicle’s computer. This signal indicates a problem with the sensor and that the systems that rely on this data may need to shut down for safety reasons.
This, of course, will have consequences. So let’s take a closer look at the most common symptoms.
What are the Symptoms of a Bad Wheel Speed Sensor?
The most common symptom of a bad wheel speed sensor is an illuminated ABS light that sometimes is accompanied by a traction or stability control light. Other common symptoms are a pulsating brake pedal, the ABS system not kicking in, or/and loss of traction or stability control.
Here’s a more detailed list that you might find helpful of the most common symptoms:
1. Warning Lights on the Dashboard
There are typically 18 standard warning lights in a car to alert you of potential issues that need to be addressed. One of these is the ABS light.
Since the wheel speed sensor monitors the ABS system, it’s also commonly one of the first signs you’ll notice as it’s triggered when the vehicle’s computer detects an issue with the wheel speed sensor. In some cases, together with a check engine light.
However, remember that many problems can cause the ABS light to illuminate, such as ABS pump issues, worn-out brake pads, low brake fluid, and more.
With that said, chances are you’ll also see the traction and stability control warning lights illuminate as they are closely connected and rely on the information from the wheel speed sensor.
Note that the appearance of these warning lights can vary depending on the make and model. Sometimes in the appearance of a sliding vehicle, other times only in text, such as “VSC OFF” or “TRAC OFF.“
When either the ABS light or all of these lights illuminate, it often means the sensor is worn out, disconnected, or clogged by debris and dirt, and you’ll have to replace it.
But sometimes your vehicle might not illuminate a light at all. So it’s also a good idea to keep an eye out for the other symptoms. But relying only on warning lights to tell you whether or not there’s an issue may be foolish.
2. Pulsating Brake Pedal While Braking
Another common symptom of a bad wheel speed sensor is a pulsating brake pedal while braking. This occurs because the sensor is not accurately measuring the wheel’s speed, causing the ABS system to engage incorrectly. As a result, the brake pedal will pulse or vibrate as the ABS tries to correct the perceived wheel speed discrepancy, even when not skidding or losing traction.
Most times, the vehicle computer will quickly detect this fault and completely deactivate the ABS, which means the pedal will go back to normal – but with no ABS there to support you.
However, it may take a few minutes for the computer to recognize this issue if you just started the car. Other times, the computer won’t recognize the faulty sensor at all, and the “pulsating” will not go away until you replace the sensor.
3. The ABS Doesn’t Kick In
It’s easy to assume that a wheel speed sensor is just another part of the modern car, but it has an important role in keeping everything running smoothly. One of those things is properly applying brake fluid when you slam the brakes to slow your car without locking up the tires.
This process is made only possible by the wheel speed sensor, which relays the speed to the ECU for the ABS system to know how much pressure to apply.
So If the sensor is not working, the ABS will be affected, which can be a safety hazard if it doesn’t kick in when needed.
Therefore, it’s important to understand that your front tires should never completely lock up. If they do, it indicates an issue with the ABS that needs to be addressed promptly. Until then, it’s recommended not to drive the vehicle.
4. Loss of Traction or Stability
Anti-lock brakes aren’t the only functions that can be affected or fail – stability control, traction control, roll stability, and hill-start assist can be compromised, too. And as we already discussed, when the sensor stops providing information, the vehicle onboard diagnostic will store a fault code. As a result, the computer will turn off these systems as well.
But shouldn’t the ABS light come on? Well, most times, yes. However, it’s not always as simple as relaying on the warning lights. Issues can still arise even if the ABS light doesn’t come on.
This means you must pay attention if you’re having difficulty keeping a grip on the road in bad or slippery weather conditions. Without a fully functioning speed sensor, you may find yourself unable to maintain control on the road. This can be dangerous and lead to serious accidents if not addressed quickly.
Is It Safe to Drive With a Faulty Wheel Speed Sensor?
Driving with a faulty wheel speed sensor is not recommended. When it fails, the vehicle’s systems that rely on this information, such as the anti-lock braking system and stability control, may not function properly. This can lead to decreased braking performance and an increased risk of losing vehicle control.
Not only does this put you in danger, but also any passengers or pedestrians who might be nearby. It would be best to address these problems before they become more serious and costly down the road.
But what causes them to malfunction in the first place? That is something we’ll take a look at next…
What Causes a Wheel Speed Sensor to Go Bad?
A wheel speed sensor can go bad because of various factors, such as regular wear and tear, harsh environment, and damage. Regular maintenance and inspections can prolong sensor life, but eventually, it may need to be replaced to ensure proper vehicle function. Let us take a closer look:
You might not think so, but human mistakes are perhaps the most common cause of wheel speed sensor failure. Replacing tires, brakes, or shocks, can sometimes lead to accidentally bending or damaging the sensor – even when the utmost caution is taken.
Age and wear
Sadly, like all mechanical and electronic parts, they are subject to wear and tear and can wear out over time. Eventually, the sensors will need to be swapped out.
However, if you’re driving with a bad wheel bearing, it can cause excessive wear and cause the sensor to not read the wheel speed correctly or at all.
Exposure to Harsh Environments
As the sensor is located in the wheel hub, it has to constantly withstand harsh environments, such as heat, moisture, and road debris. This will, without a doubt, have a hard turn on the sensor, eventually causing it to go bad.
How do You Diagnose a Faulty Wheel Speed Sensor?
Diagnosing a faulty wheel speed sensor can be like searching for a needle in a haystack if you don’t know what to do or look for. However, the process itself isn’t often overly complicated. Here’s what you want to do:
1. Check Trouble Codes
You may have been recommended to start by visually inspecting the sensors. Sure, it can reveal a lot. However, most times, this method won’t give you any answers at all.
To save time and effort, the best approach is to use a code reader to check for any stored trouble codes. This will often tell you where the problem is and what the problem is, such as “Left front ABS solenoid 1 circuit malfunction.”
2. Read Live Data
While spinning the wheel or driving your vehicle (with the help of a passenger), you can have an OBD reader connected to read live data parameters for the ABS sensor, such as output voltage or speed. An erratic reading may indicate that one of your wheel speed sensors is malfunctioning and needs to be replaced.
Both methods above are quick ways to diagnose and pinpoint any issues with the sensor or the wheel speed sensor circuit.
Depending on the output and what information the trouble codes give you, you can take the appropriate action and won’t spend time and money replacing the wrong sensor.
How to Replace a Wheel Speed Sensor
Replacing a wheel speed sensor can seem like a daunting task, but with the right tools and knowledge, it can be done relatively easily.
Here is a step-by-step guide on how to replace a wheel speed sensor:
- First, remove the tire from the vehicle. This will provide better access to the sensor.
- Next, locate the sensor. It is typically located on the hub assembly or the steering knuckle. It is often a small, cylindrical sensor with wires coming out of it.
- Disconnect the sensor’s electrical connector. This is typically done by squeezing the connector’s tab and pulling it off.
- Locate the sensor’s mounting bolts or clips. These will vary depending on the vehicle’s make and model, but they are usually located near the sensor’s base.
- Remove the sensor’s mounting bolts or clips using a socket wrench or pliers. Carefully pull the sensor out of its mounting location.
- Inspect the sensor for any visible damage or wear. If the sensor looks damaged, it should be replaced.
- Install the new sensor in the reverse order of removal. Make sure to properly connect the electrical connector and securely fasten any mounting bolts or clips.
- Finally, re-install the tire and test drive the vehicle to ensure proper sensor operation.
It’s important to note that, before starting this process, make sure you have the correct sensor for your make and model of car.
Cost of Replacing a Wheel Speed Sensor
When a problem arises, it’s almost uncanny how quickly our minds inevitably wander to what it will take to get us back on track again. But I guess it’s in our nature. In this case, we’re talking about replacing a wheel speed sensor – so let’s consider how much that might set you back.
Generally, you can expect to spend anywhere from $150 to $400 for parts and labor. The part itself costs about $100 to $200, and labor costs another $100 to $300. The cost can, of course, vary depending on the car and model and year of the vehicle, but also repair shop location and parts quality.
Additionally, by going with an OEM replacement part that lasts longer, you can expect to pay more than if you opt for an aftermarket version.
No matter which option you choose, it’s important to consider other factors, such as warranty coverage or how long it will take for your order to arrive, before making a purchase decision.
Can You Prevent a Wheel Speed Sensor From Going Bad?
It’s difficult to take any action regarding matters beyond our control, such as most general wear and tear. However, some things can be done to prevent a wheel speed sensor from going bad.
The first and most important step is to maintain your vehicle regularly. In this case, I’m not talking about regularly changing oil or spark plugs – which you should also do. But I am talking about regularly inspecting your vehicle’s brakes, suspension parts, and other components connected to your wheel hub.
I know many people go years without doing so, but you can avoid a lot of trouble if you take 5 to 10 minutes extra time to check these things when you rotate the tires (which you should do every 5,000 to 7,500 miles to avoid uneven wear).
Another thing to remember is to be careful not to physically damage the connector or wiring while working on the brakes or changing tires.
And finally, like usual, avoid driving through deep puddles, heavy mud, or on rough or bumpy roads.
Frequently Asked Questions
How do I Know If My Wheel Speed Sensor Is Going Bad?
A few ways of telling if your wheel speed sensor is going bad are an illuminated ABS light that sometimes is accompanied by a traction or stability control light, a pulsating brake pedal, the ABS system not kicking in, or loss of traction or stability. Check for trouble codes or measure live data to make sure.
What are the Common Causes of a Bad Wheel Speed Sensor?
The most common causes of a bad wheel speed sensor include accidental damage to the sensor’s wiring or connector, dirt or debris clogging the sensor, or damage to the sensor itself due to general wear and tear. The sensor can sometimes be cleaned if dirty, but most times, you need to replace it to fix the problem.
Can I drive With a Bad Wheel Speed Sensor?
You can drive with a bad wheel speed sensor. However, it’s not recommended since it often means critical safety systems such as the ABS (anti-lock brake system) or/and traction and stability control systems could be off. This means you must maintain control of your vehicle during brakes or loss of traction.
Can ABS Sensors be Cleaned?
ABS sensors can be cleaned, but it’s important to be cautious in doing so. Dirt and debris can accumulate on the sensors over time and cause them to malfunction. To clean it, remove the sensor, take your rag and wipe the sensor clean of debris, preferably without using chemicals. If necessary, use mild soap and rinse.
Does the ABS Sensor Affect Acceleration?
Yes, if an ABS sensor is faulty, it can sometimes affect acceleration. As an example, if the traction control thinks you are skidding, even tho you’re not, it can affect the engine throttle and also the transmission as it tries to keep the car out of a skid. What you want to do is to check for related trouble codes.
Can a Bad Wheel Speed Sensor Cause Transmission Problems?
A wheel speed sensor doesn’t per se cause transmission problems. However, some automatic transmissions rely on the vehicle’s speed calculated from the ABS sensor to shift gear. This, in turn, might cause the issue you’re referring to as transmission problems. To confirm this, check for trouble codes.
Will a Bad ABS Sensor Cause the Speedometer Not to Work?
A bad ABS sensor can cause the speedometer not to work, as it is responsible for measuring the wheel speed and sending this information to the vehicle’s computer. From the data, the computer then calculates the speed. So if it malfunctions, the speedometer won’t get accurate information and won’t function properly.