7 Bad Speed Sensor Symptoms & Replacement Cost

Find out if you’re overpaying on car insurance using our cost calculator! Save money by comparing quotes from over 30 of Canada’s top insurance providers!

The best part? It’s FREE!

bad speed sensor symptoms

You’re driving down the highway on your daily trip to work; suddenly, you hear a cop’s mobile siren. You pulled over, and the police officer warned you that you exceeded your local speed limit by 10 miles.

You clarify that your speedometer indicated an incorrect reading, but the officer doesn’t believe you and issues you a penalty ticket on the spot. What a hassle, right? If this has occurred in your vehicle, it might be due to a faulty speed sensor.

Nowadays, automobiles are equipped with a plethora of various systems and sensors. Generally, such components are pretty beneficial and assist your engine control unit (ECU) in keeping your automobile running effectively and smoothly.

Unfortunately, when one of such sensors fails to function correctly for any cause, it could have a significant impact on your vehicle’s overall performance. As its name indicates, the vehicle speed sensors or transmission speed sensor within your automobile is essential for calculating the speed at which your vehicle is running.

A faulty sensor might manifest itself in various ways, involving incorrect or erratic speedometer readings, automatic transmission difficulties, and issues activating your cruise control. Today, we’ll take a detailed look at what a speed sensor is, the bad speed sensor symptoms, and other informative and helpful details regarding your speed sensor. Read on to learn more!

Faulty Speed Sensor Symptoms

  • Transmission Issues
  • Irregular Speedometer Readings
  • Cruise Control Failure
  • Acceleration Issues
  • Hard Braking
  • Transmission Torque Converter Clutch Application Trouble
  • Check Engine Light

What Is A Speed Sensor?

The speed sensor within your automobile, sometimes referred to as the wheel speed sensor, vehicle speed sensor, or transmission speed sensor is a sort of speedometer or tachometer that sends data to your car’s computer, informing it of your vehicle’s speed.

The computer subsequently adjusts your RPMs, speedometer, and, most significantly, your gearbox shift positions based on its data. Your vehicle speed sensor locations are different in every vehicle. However, it is often located on or near your transmission. If you can’t locate it, consult your owner’s handbook for its precise location.

How Does A Speed Sensor Operate?

A vehicle’s speed sensor operates by measuring the rotations of your wheels. This is accomplished by measuring the cycles of a toothed wheel mounted on your transmission shaft. Whenever your transmission shaft is rotated, your sensor is engaged.

A sprocket connects to your engine’s crankshaft or transmission’s output shaft. When this shaft spins, its sprocket attached to it also revolves. A few of its teeth on your wheel are exposed. As your wheel goes past the sensor, your speed sensor detects the data from every tooth.

Your sensor determines whether a complete rotation has occurred by seeing the open teeth. After that rotation, all data is transferred to the ECU or engine control unit, which uses it to compute your overall speed. Your tachometer then displays the results.

A speed sensor was initially employed to substitute the cable connecting vehicle road wheels to your speedometer; this eliminated cable breakage and improved the gage’s operation. Whereas traditional speedometers include several moving elements, your speed sensors feature merely a needle spring.

The majority of speed sensors consist of a metal-toned rotor and a sensor. Passive or active sensors are available. The passive speed sensor generates an Alternating Current (AC) output that varies in rhythm by your wheel’s motion.

Your wheel should spin quickly enough to generate the AC output. As a result, they can’t sense signals traveling less than 2 miles per hour. Due to the inability of passive wheel sensors to interpret data at low speeds, most automakers opted for the active speed sensor.

An ABS module supplies electromotive power for an active speed sensor. This module operates between 8 to 10 volts and alters these voltages by approximately 0.6 and 1.2 volts.

Faulty Speed Sensor Symptoms

Nowadays, most automobiles depend on speed sensors to regulate or monitor the engine system. Once your speed sensor fails, it might give wrong signals and data to your vehicle’s computer, causing various problems.

A defective speed sensor might result in multiple speed sensor issues, including the following symptoms below.

Gear Shifting Problems

The transmission control module or TCM, or others call it powertrain control module or PCM, uses your car speed data received by your speed sensor to calculate and determine shift timing. As a result, a failed speed sensor would have a significant effect on the functioning of your automatic gearbox.

Any malfunctioning transmission speed sensors will be unable to deliver reliable speed readings. Once this occurs, your car’s computer can’t operate your transmission’s gear shifting. This might cause the gearbox to shift gears more quickly and harshly than usual.

Speed sensor issues could potentially impact the shift timing, increasing intervals in transmission shifts. A hydraulically operated automatic transmission is developed and engineered to shift smoothly and perfectly.

If it shifts abruptly, it could damage internal components such as valve bodies, mechanical gears, and hydraulic lines. It would help if you got your car inspected once you detect your transmission is shifting irregularly to avoid these issues.

Irregular Speedometer Readings

Numerous automobiles utilize vehicle speed sensors as a primary source for speedometer operation. Once your speed sensor fails, your speedometer might display an irregular value or, in some cases, no measurement at all.

While you can run your car without a functional speedometer, not seeing how fast you’re traveling makes driving more complicated and dangerous. It might result in conflict with the law, mainly if your area has enforced speed restrictions.

Additionally, it might result in accidents and other complications. If your speedometer unexpectedly stops working, this is an indicator of a bad wheel speed sensor. Your speed sensor could no longer indicate your car’s running speed. It’s essential to get it fixed as soon as possible.

Cruise Control Failure

Due to your sensors’ tracking of the input shaft speed sensor and output shaft speed sensor rates, your speed sensors also assist in managing your vehicle’s cruise control. Faulty speed sensors can’t transmit correct data to your vehicle’s computer, causing the computer to deliver an error code to your ECU or engine unit control unit. This might cause your ECU to deactivate its cruise control as a preventive step.

This occurs because the system would require your speed sensor data to maintain a constant speed for your vehicle. As a result, when your speed sensor ceases to transmit the data to your vehicle’s computerized systems, your cruise control is disengaged instantly.

As soon as you discover a problem with your car’s cruise control, including failing to engage when you push its button, get it examined and repaired by your mechanic to verify if a defective speed sensor triggered the problem.

Acceleration Issues

If you feel your automobile slowing while you accelerate and experiencing difficulties overtaking other vehicles on the freeway, this might result from a defective engine speed sensor. Your ECU can’t compute the correct amount of fuel to feed into your cylinders whenever your speed sensor isn’t operating correctly.

This results in a decrease in power and the inability to overtake other vehicles. This symptom could also be induced by various other issues, which is why it’s critical to get your automobile inspected by a mechanic.

Hard Braking

Another often seen sign of a malfunctioning or defective speed sensor is difficulty applying your brakes. If your brake pedals are very challenging to press down, the speed sensors are likely faulty and need repair or replacement.

Transmission Torque Converter Clutch Application Trouble

One of the most often encountered vehicle speed sensor issues is the torque converter within your vehicle’s transmission system failing to engage its clutch and establish a mechanical connection between your car’s transmission and engine.

This could occur when your car’s speed sensor fails to provide accurate reading to its computer since your torque converter is triggered at a certain speed. Additionally, this exact issue might result in other problems such as slippage, increased fuel consumption, and transmission overheating.

Check Engine Light

Your ECU or engine control unit can illuminate your check engine light, plus generate a diagnostic trouble code if your speed sensor inputs are missing. Your check engine light could also illuminate if your vehicle’s computer detects that your exhaust emissions are escalating and exceeding the permissible levels for air pollutants.

Link your car to an OBD-II scan tool to determine what caused your check engine warning light to appear. After determining and resolving your speed sensor issue, your technician should reset the fault codes.

Causes Of Speed Sensor Failure

Speed sensor failures might trigger a slew of other difficulties in your car. You might now be capable of identifying the signs and symptoms of a bad speed sensor, but how do speed sensors screw up? The following are some of the possible causes of a speed sensor failure.

Electrical Trouble

Internal electrical fault to speed sensors might occur throughout time. This might manifest in an abnormal output signal or the absence of any output at all.

Poor Maintenance

According to experts and responsible car owners, good automotive maintenance and management can significantly increase the lifetime of your vehicle and its system components. Adhering to the suggested maintenance plan can also assist in extending the lifespan of your speed sensor.

Failure to do so increases the likelihood of speed sensor degradation, resulting in speed sensor difficulties with your car. If your sensors’ components get clogged with muck, dirt, or any fluid pollutants, they will not provide reliable and accurate data.

Loose or Damaged Wiring Connections

Disconnecting your sensor from your ECU or engine control unit might also create complications. Ensure that no connections are damaged or loose. Additionally, inspect for corrosion and dirt accumulation.

Wear and Tear

The sensor itself is susceptible to breakage or cracking. Additionally, its plastic component might develop brittleness as it’s exposed to the environment. The magnetic component of your speed sensor might ultimately get worn or broken.

Failing Speed Sensor Diagnosis and Fixing

Once your car begins to exhibit the signs of a malfunctioning speed sensor, as detailed above, it’s critical to schedule time to examine your vehicle to see whether your speed sensor is indeed the issue.

A multimeter may assist in simplifying the diagnostic. This technique would also be beneficial for individuals curious about how to check the speed sensors.

Step 1: Park Your Car

To begin, park your vehicle on a flat and safe surface. A flat and smooth surface makes it easy to reach your speed sensor easily. Then, switch off your car and any other connected components, including the lights.

Step 2: Find Your Speed Sensor

Lift your vehicle’s hood and look for your wheel speed sensor around the gearbox. Carefully locate the dipstick on your transmission and trace it down to your sensor, which is attached to your transmission via two wires with black and white colors that are held by a metal brace.

However, the placement of various vehicle speed sensors may vary, so it is necessary to consult your car’s manufacturer’s handbook for confirmation.

Step 3: Unplug The Harness and Take Your Sensor

Disconnect the white and black wires from your wheel speed sensor and retrieve it using a screwdriver or pliers. Additionally, you might disconnect and uninstall them using your fingertips. Then locate and click a button or clip on the top or side of your wheel speed sensor to unlock it.

Additionally, determine if any bolts or screws must be loosened before removing your sensor. Then, slowly wriggle or move your sensor from its place. Avoid yanking it off to avoid damaging it.

Step 4: Attach The Wires To A Multimeter

The black wire must be connected to the black terminal, while its white wire should be connected to its red terminal. Then, carefully insert the cables into the slots, making sure they snap entirely into position. Then, by adjusting the dial, set your multimeter into alternating current  (AC.)

Step 5: Plug Your Sensor Into Your Car

The sensor is connected to the car through white and black cables. This wire could be purchased at an auto accessory store which comprises a white output signal and black ground cable. Securely connect them to your sensor.

Step 6: Attach The Black Lead To The Exposed Wire

Attach the exposed cable to the black lead attached to your speed sensor. Then, link the sensor’s white wire to the red wire.

Step 7: Connect A Drill Bit To Check Your Sensor

Get a drill bit that’ll be utilized to simulate the sensor’s motion at this phase. Select a drill bit that slips snugly into your speed sensor and spin the gear within.

Attach your drill bit to your power drill and secure it carefully not to come off. Then, using your drill, spin your speed sensor. Begin spinning gently and gradually raise the speed till a precise reading is obtained.

Step 8: Determine The Multimeter Reading

Once you begin rotating your speed sensor using your drill, observe whether the figure on your multimeter rises according to the speed; when it does, your sensor is in good condition. However, your sensor is defective if it doesn’t increase in response to speed or refuses to indicate any voltage.

When you have a faulty speed sensor, it’s essential to replace it immediately. Make sure that you get one compatible with your car’s requirements.

Can You Drive A Car With A Faulty Speed Sensor?

You might definitely get away by running your vehicle with a malfunctioning speed sensor for a short period, particularly if you’re only taking it to the service shop. But, it is not a great thing to continue driving without a functional speed sensor for much longer than necessary.

Apart from the issue that you’re unable to know how much speed you’re running without a working speed sensor, a defective speed sensor might create interference with the functioning of your transmission and might induce damage to it.

Finally, not only are you risking damage to your automobile by running without a functioning speed sensor. You could also jeopardize your safety. If you believe your sensor is faulty, you must get it serviced immediately.

Speed Sensor Replacement Cost

The typical cost of replacing your speed sensor is around $220 to $236. Labor expenses are projected to be approximately $62 to $78 per hour, while components cost $157. However, in other cases, this might cost more.

That is still not excessive when you realize that difficulties with this component might result in you losing control of your car and causing a catastrophe. Also, this price range varies depending on your vehicle’s make and model, year, mechanic shop, and location.


Perhaps, this article clarifies the symptoms of a faulty speed sensor and other speed sensor-related concerns. If you feel the diagnosing procedure is difficult or too complicated, seek the assistance of a professional.

Additionally, we’d recommend that you attempt to resolve any issues with your vehicle as quickly as possible. It’s preferable to respond pro-actively to avoid the minor defect escalating and becoming a more expensive repair. Best of luck!


Is a wheel speed sensor the same as an anti-lock braking system or ABS sensor?

Yes! Your ABS sensor is referred to as the ABS brake sensor or the wheel speed sensor. Since not all wheels spin at an identical pace, your ABS sensors transmit the speeds of all your wheels towards your ECM, which decides if your wheels are locking up.

What leads a speed sensor to fail?

Throughout time, your transmission speed sensor might become defective owing to wiring difficulties or simply fail due to its regular usage while driving your car. If your sensor comprises magnetic, it might fail due to iron adhering to your sensor’s tip, resulting in an incorrect measurement.

How many speed sensors does an automobile have?

On most automobiles manufactured in the previous few decades, 4 wheel speed sensors are installed – 1 per wheel. The ABS system uses the data from such sensors to assess how rapidly the automobile is slowing.

Sign up for our Newsletter

Related Articles