Blog Car Care Advice Speed Sensors: Ultimate Guide (2021)
Car Care Advice

Speed Sensors: Ultimate Guide (2021)

March 25, 2021
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Want to learn more about the speed sensor in your car?

The speed sensor is a small device that tells your car’s speedometer how fast you’re going. It plays a role in your car’s transmission and cruise control systems.

In this article, we’ll cover what a speed sensor is and how it works. Then, we’ll look at the symptoms of a defective speed sensor and how often you should replace it.

Finally, we’ll go through the steps involved in replacing the sensor and highlight the best way to keep your speed sensors in check.

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Let’s jump right in.

What Is A Speed Sensor?

A vehicle speed sensor (VSS) is a small component mounted on your car’s transmission that lets the car’s onboard computer know how fast you’re moving.

It’s also known as a wheel speed sensor, transmission speed sensor, or output shaft speed sensor.

How does the speed sensor work?

The vehicle speed sensor measures the rotational speed of the gears in your transmission system. Then, it converts this measurement into an analog signal or a low voltage square wave signal and relays it to electronic control units (ECUs) inside your car.

In turn, the ECUs use this signal to adjust your car’s speedometer readings, the ABS module, and transmission system.

Your car’s cruise control system may also rely on data generated by the speed sensor. Without it, your car wouldn’t be able to maintain a constant vehicle speed.

What Are The Symptoms Of A Faulty Speed Sensor?

Since your car’s speedometer readings, transmission systems, and cruise control depend on signals from the speed sensor, you need to ensure that it’s working as expected.

If you experience any of these symptoms while driving, you might need to get the vehicle speed sensor inspected and replaced:

1. Inconsistent Speedometer Readings

Most cars depend on signals from the wheel speed sensor to adjust their speedometer readings. A faulty sensor can result in inconsistent or erratic speedometer readings.

Alternatively, it can result in no readings at all.

This doesn’t mean that your car would simply stop working and you can’t drive it anymore.

However, with a malfunctioning speedometer, you’ll have no clue about how fast your car’s going, which can compromise your road safety.

If you notice that the speedometer is acting odd, consider getting your car inspected by a mechanic to check for any speed sensor failures.

2. The Check Engine Light Gets Activated

If the Check Engine Light on your car’s dashboard gets illuminated, it can be due to a variety of reasons, like:

However, it can also signal a defective speed sensor.

With a faulty speed sensor, an electronic control unit within your car might fail to detect a transmission speed sensor signal. And this error can activate your car’s engine light.

In such a situation, it’s best to take your car to a mechanic for an inspection.

3. Malfunctioning Cruise Control

In most cars, the cruise control system depends on input signals from the transmission speed sensor.

So if you’ve got a faulty speed sensor, you probably won’t be able to engage the car’s cruise control.


Generally, the powertrain control module (PCM) inside your car automatically disables cruise control when it fails to receive a proper signal from the VSS. 

It does so because it’s impossible to maintain the constant vehicle speed needed for cruise control without transmission speed sensor data.

When you notice that the cruise control system in your car is malfunctioning, have a mechanic come over to check if you’ve got a speed sensor problem.

4. Harsh Transmission Shifting

Without a reliable signal coming in from the transmission speed sensor, the powertrain control module can’t correctly shift the gears within your transmission system.

What does that result in?

The PCM can cause rough gear shifts and impact the timing between your transmission shifts.

That’s not all.

If your car uses an automatic transmission system, a faulty sensor can also cause severe damage to the mechanical gear tooth profile and other internal components like hydraulic lines, valve bodies, and more.

To be safe, consider getting a car inspection soon to identify any transmission problems your vehicle might have.

How Often Should You Replace The Vehicle Speed Sensor?

There’s no hard-and-fast rule to help you predict how long your wheel speed sensor is going to last.

Unlike a brake light switch or brake caliper that can last as long as your vehicle, you can expect your transmission speed sensor to last between 30,000 and 50,000 miles.

However, as is the case for brake pads, your speed sensor’s life also depends significantly on your driving conditions. If the speed sensor suffers frequent exposure to road salt and other compounds, it won’t last as long.

Moreover, the following conditions may also decrease the lifetime of your vehicle speed sensor:

To prevent safety hazards, if you notice symptoms like erratic speedometer readings or malfunctioning cruise control, consider getting your VSS inspected ASAP and have it replaced if found defective.

How Much Does A Speed Sensor Replacement Cost?

The cost of replacing the speed sensor depends on the make and model of your vehicle. It also depends on the type of sensor currently used, such as an optical sensor, magnetic field sensor (Hall effect sensor), or another type.

However, speed sensor replacement isn’t generally expensive. It won’t cost more than other significant repairs like brake line and master cylinder replacements. 

With that being said, chances are you’ll have to pay between $225 and $380 to replace the vehicle speed sensor.

To get a more accurate estimate, just fill this online form.

How To Replace Your Car’s Speed Sensor

You can try to replace your car’s wheel speed sensor by yourself. 

But we highly recommend seeking help from a skilled technician.


For starters, you’ll need multiple tools and safety equipment to carry out the vehicle speed sensor replacement safely.

And these include:

Besides, if you don’t perform the replacement the right way, you could end up with a malfunctioning speedometer or cruise control system, which can compromise your road safety and result in more repair costs.

It’s always better to take your car to an auto repair shop or have a mobile mechanic come over.

When hiring a mechanic, remember to verify that they’re:

For an idea of what the speed sensor replacement usually involves, here’s a breakdown of what your mechanic will likely do:

1. Slide a drain pan or bucket under the sensor to collect any leaking fluids.

2. Gently disconnect the vehicle speed sensor from the transmission system.

3. Remove the connector between the car’s wiring and speed sensor.

4. Loosen and remove the defective speed sensor with a socket wrench.

5. Install the new speed sensor and reconnect it to the wiring.

6. Start the car’s engine and take your car for a test drive to ensure that the speedometer, cruise control system, and transmission shifting work as expected.

But where can you find a qualified mechanic who can perform a proper speed sensor inspection and replacement?

The Best Way To Keep Your Speed Sensor In Check: RepairSmith

If you’re looking for an easy way to repair your speed sensor, look no further than RepairSmith, a convenient and mobile car repair and maintenance solution.

Here’s why you should rely on RepairSmith for all your speed sensor needs:

Keep Your Speed Sensor Up To Speed

The vehicle speed sensor is a critical component that ensures that your speedometer, cruise control, and transmission works well.

If you’re driving around with a defective speed sensor, you may not know how fast you’re going and can compromise your safety and those around you. Moreover, you’ll likely have a poor driving experience due to harsh and irregular transmission shifting.

To prevent this from happening, hire a mechanic to inspect your wheel speed sensor and perform a replacement if necessary.

Fortunately, RepairSmith makes hiring mobile technicians easier than ever!

All you have to do is fill an online form, and certified mobile mechanics will come to your driveway to perform speed sensor inspection and replacement.

So, if you’re looking for a hassle-free and accessible repair service for speed sensor requirements, contact RepairSmith today!