Speed Sensor Symptoms

Speed Sensor Symptoms – How Can You Know If It’s Gone Bad?

You may not be aware of speed sensor symptoms, but you may encounter them while driving. The traction control and ABS lights may suddenly light up, or your vehicle may become sluggish for no apparent reason. The lights may go out on their own, but they will turn back on after a few minutes. The transmission may appear to be stuck at a specific speed, preventing you from accelerating.

All these are speed sensor symptoms, and this article will provide you with all the information that you need to know.

What Is A Speed Sensor

The speed sensor is an important component of the car’s engine. Without it, the engine would not know when to shift gears, which could lead to damage. There are various speed sensor symptoms that can reveal that there is an issue.

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The sensor is usually located behind the wheel and detects changes in wheel rotation. This creates voltage, which is then sent to the computer. The computer uses this information to determine how fast you are going.

How Does A Speed Sensor Work?

The sensor collects and transmits information about the vehicle’s speed to the ECU. The ECU uses this data to optimize the movement of various parts of the vehicle.

This includes the amount of air and fuel used in combustion, as well as transmission shifts. It also controls the ignition timing as well as the precise time of injection. The same data is used to calculate gear changes.

Sometimes one of the wheels will begin to move faster than the others. This is the point at which the sensor takes action by sending the data to the engine. The inputs assist the ABS in planning its actions.

Other components, such as the transmission, brakes, and axles, are also regulated. The speedometer also uses the inputs to display the correct speed and distance.

The system consists of two sensors that work together to transmit accurate data. They are referred to as input and output shaft sensors. Any speed sensor problems will involve one or both of these sensors.

What Are Bad Speed Sensor Symptoms

When these sensors fail, you may experience sudden acceleration. You may also see inconsistent speed readings on your dashboard. Given below is a list of the most common speed sensor symptoms:

1. Difficulty In Changing Gears

If you find changing gears difficult, it means that there is a problem with the speed sensors. The speed sensor converts the transmission’s rotation into a voltage on the signal wires that correspond to the engine speed.

The analog signal is then routed through differential gears to the flywheel input shafts, engaging the clutch discs. There will be some slippage between these components if any are damaged or worn.

Sometimes, these sensors get dirty or wet, which could cause transmission issues.

2. Speedometer Not Working

You might find your speedometer showing that you’re traveling faster than you are. The speedometer needle is set to 40 miles per hour, but the car might not be moving at all. These are symptoms indicating that your speed sensor is damaged.

Speed Sensor Symptoms

A faulty sensor can provide inaccurate vehicle speed readings, causing drivers to make poor driving decisions. Either the sensor is not communicating with the ECU or it is sending incorrect data to the ECU. You may also need to replace the sensor cable, which would mean you need to buy a new one.

3. Check Engine Light Turns On With A Bad Speed Sensor

A check engine light indicates a problem with the car’s speed sensor. A sensor’s main job is to measure the car’s speed. Its failure or any problem with its signal can cause inconsistent idle or low power output. Your car may be unable to sustain cruising speed.

An object in the path of a vehicle’s alarm system may also cause the check engine light to glow.

4. Cruise Control Not Engaging

If your car’s cruise control is not engaging, it could be a sign of a speed sensor issue. Cruise control allows you to maintain a set speed. Some sensors can tell when the car’s speed changes. This lets the cruise control set the car’s speed.

The speed sensor measures wheel rotation and communicates that information to the ECU. It can sometimes fail to engage cruise control. The speed sensor tells cruise control how quickly to move and when to slow down. If this sensor isn’t working properly, the car may constantly accelerate or stop moving.

5. Torque Converter Clutch Issue

The vehicle’s speed sensors activate the torque converter clutch at a preset speed. However, these sensors are unable to transfer the torque converter onto the clutch, which is critical for the car.

The clutch and the torque converter cannot establish a smooth and mechanically linked relationship. Slipping, lower fuel economy and an overheated transmission can all result from this problem.

6. ABS Light Activated

The ABS light comes on when the speed sensor malfunctions. This implies that the car has no way of knowing how fast or slow it is traveling, and hence cannot brake properly.

The ABS light indicates a malfunctioning speed sensor. The speed sensor monitors wheel rotation and sends it to other electrical components of the vehicle, which sends it to the engine control module. A broken speed sensor can’t deliver precise signals to other sections of the car’s electronics.

7. Stability Control Light On

A speed sensor malfunction causes the traction control light to come on. It’s usually an electronics issue, but it might also be a speed sensor problem. A traction or stability control light indicates a speed sensor malfunction.

The traction or stability control light comes on when the engine reaches a certain RPM due to a speed sensor malfunction.

8. Bad Speed Sensor And Sluggish Acceleration

A faulty speed sensor may transmit erroneous indications to the engine’s computer. These sensors tell a car’s computer how fast to accelerate. If this sensor doesn’t work, the car might not know when it needs to speed up, making it slow.

Causes Of A Bad Speed Sensor

The speed sensor measures the car’s speed. The sensor sends this data to the computer, which calculates how much fuel to utilize. There are several reasons why your car’s speed sensor may malfunction.

Speed Sensor Symptoms

1. Low Voltage

Low battery voltage can cause problems with the speed sensor. The speed sensor tells the car’s computer how fast the engine is operating. A damaged battery can generate a weak transmitting signal. The engine RPM may not be checked effectively, resulting in erroneous speed estimates.

2. Electrical Fault

A car’s internal electrical issues might cause speed sensors to malfunction and read incorrect data. This is usually caused by poor wiring and connections, which can be fixed by replacing the sensor or repairing the sensor wire harness.

The ECU uses the speed sensor to calculate the engine’s output speed. Having a bad speed sensor will make it hard to get the throttle to open quickly, and it could also cause the engine to misfire because the speed sensor doesn’t work.

3. Wear And Tear Of Speed Sensors

The car’s computer takes inputs from the sensor’s data. It may not be able to accurately determine speed due to the sensor’s wear and tear. The sensor can’t calculate speed accurately enough for cruise control or anti-lock brakes.

Incorrectly functioning sensors may fail to detect differences in driving speeds. This will lead to the car going too fast or too slowly.

4. Poor Maintenance

While misdiagnosing speed sensor faults is possible, poor vehicle maintenance can lead to issues over time. Neglect or poor care can cause sensors to break down, which sends the ECU the wrong signals.

5. Broken Wiring Or Bad Connections

A broken wire or a bad connection can cause a speed sensor issue. A signal break may be caused by a wiring fault. This will hinder signal transmission between components.

Poorly installed connections can also cause this. They might not be able to transmit the correct voltage or let too much voltage out, which could cause a break in the signal.

6. Dirty Connections

Dirty connections might create speed sensor issues since they impact the signal. Sand or mud in the wiring could cause this.

7. Metal Objects Near Speed Sensors

Metal objects near the sensor may cause a speed sensor issue. Magnetic fields can mess with sensor readings and change the signal sent to the computer, which can lead to inaccurate data.

To get an accurate assessment, the sensor’s signals must not be disturbed. Anything touching or close by can interfere with the signal and cause false readings.

8. Moisture

Moisture can cause a problem with a car’s speed sensor. When moisture gets into the case of a sensor, it can make the sensor faulty. Condensation or precipitation from a humid environment can also affect the sensor.

9. Low Tire Pressure

Low tire pressure could be another cause of a speed sensor issue. Tires must be inflated to prevent sensor distortion when measuring vehicle movement. If the tires are under-inflated, the sensors will have a hard time figuring out where things are moving and may not work at all.

10. Speed Sensor Damage

A malfunction in the speed sensor can be caused by damage to the sensor itself. This can be due to an object hitting or passing close to the sensor, or corrosion of the electrical connections.

How Can I Fix A Bad Speed Sensor?

Your vehicle may be experiencing speed sensor symptoms. So how do you test a speed sensor? It’s not too difficult, and if you have a multimeter, you can perform the test yourself.

  1. Check for error codes related to the transmission speed sensor using an OBD-II scanner. If a relevant error code is displayed on the scanner, replace the sensor.
  2. First, make sure your vehicle is on a level surface. This will allow you to get to the sensor without too much difficulty.
  3. Then turn off the engine and any other lights that may be on. Also, turn off anything that uses battery power.
  4. To be completely safe, remove the ignition key as well.
  5. Look under the hood for the speed sensor. The exact location of the sensor is determined by the make and model of your vehicle. It is usually found near the transmission in most cars. You can also consult your owner’s manual for more information on the location.
  6. Following the dipstick is an easy way to locate the speed sensor. The sensor is a small device contained within a metal case.
  7. It’s linked to the transmission via black and white wires. One wire serves as a ground, while the other sends the signal to the car’s computer.
  8. You must first disconnect the cables before removing the sensor. Remove the cables with a pair of pliers.

Taking Out The Speed Sensor

  1. By pressing a small button and pulling it out, you can remove the sensor from its case.
  2. If it is too tight, you may need to gently shake it to get it out. At the same time, don’t use too much force, or you’ll end up damaging it.
  3. Before removing the sensor, check for any screws that need to be removed.
  4. Now connect the multimeter. The black and red wires must be connected to terminals of the same color. You will know that it is connected when you hear a clicking sound.

Speed Sensor Symptoms

Using A Multimeter

  1. Before using the multimeter, set it to alternating current.
  2. The speed sensor is plugged into a slot. The black and white wires must be connected to the sensor wires.
  3. To test the speed sensor, you must create movement within it. A drill bit can be used to accomplish this. The drill bit must be the correct size to be connected.
  4. You can move the sensor once it is connected. Before you get a correct reading, it should spin as fast as it can.
  5. Begin slowly and gradually increase your speed. Take note of the reading once and then again when the speed is increased.
  6. When the speed increases, the reading should also increase.
  7. If the reading does not increase with speed, it indicates a speed sensor symptom.
  8. Once you’ve determined that there is a problem, replace the sensor.
  9. Check for the same specifications before replacing it with a new one.
  10. Once you have installed a new sensor, do a test drive to ensure that it is working.

The steps described above will make it easy for you to identify speed sensor symptoms. You can save money by checking the sensor yourself. Then you can replace it with a new one if it is defective.

You will need the appropriate tools to carry out the work yourself, given in the next section.

Safety and Tools While Replacing A Speed Sensor

Replacing a car’s speed sensor may appear simple, but you must take precautions to avoid injury.

The car’s speed sensor is located inside the car’s engine. It is not easily accessible and to get to it, you will need to remove wires and other components.


This is an important tool with which you can check for a faulty sensor. You can also use it when you replace a car’s speed sensor with a new one. Use the multimeter’s two probes to check the voltage at the sensor’s connection points to make sure there is no short.


Pliers come in handy because of their tight grip on nuts and bolts. You will also need them for disconnecting wires from their connectors.

Socket Wrench

This will enable you to unscrew bolts easily.

New Speed Sensors

You must ensure that the new sensors have the same specifications as the old ones.

Mechanic Gloves

Rubber mechanic’s gloves protect the hands from sharp bolts and glass shards when replacing speed sensors. They protect against harmful chemicals like battery acid and petroleum byproducts as well. Another advantage is that these gloves improve your grip while working.

Long Sleeve Shirt

Heat exposure while working on a car’s speed sensor can be very harmful. Wearing long-sleeve shirts protects you from the hot engine and prevents burns. Long sleeves also protect you from accidental injuries. It protects your skin from oily and greasy equipment as well.

Eye Protection

Working on a car exposes you to a lot of dust and debris, so you must protect your eyes. When removing or replacing a vehicle’s speed sensor, avoid getting metal and grease particles in your eyes.

Flat Surface

You will need a flat working surface for this task. So, make sure that your garage or your driveway does not have any undulations.


You might have questions pertaining to replacing speed sensors, as given below:

What If I Do Not Replace The Speed Sensors

Driving with a faulty speed sensor is extremely dangerous. The sensor measures the vehicle’s speed to determine when to apply the brakes.

When a speed sensor fails, the computer is unable to determine when to increase engine power or apply the brakes. A faulty system could result in a fatal accident.

Replace a bad speed sensor as soon as possible to prevent further damage to your vehicle.

The speed sensor also controls the anti-lock braking system. The ABS may fail if you drive with a faulty speed sensor.

It can also lead to a loss of braking power and a collision. The transmission behaves erratically due to a bad speed sensor.

Can A Faulty Speed Sensor Cause Low Engine Power?

A faulty wheel speed sensor can cause a vehicle to misread the speed of a tire. This will result in reduced engine power, a lack of traction, and braking difficulty.

The car’s engine control unit controls the engine by sending data to the throttle control system. The system regulates the amount of gas used to keep the engine running at the desired speed.

When the sensor data is incorrect, the computer may compensate by readjusting fuel or throttle inputs. This will cause a loss of power.

How Often Do Speed Sensors Fail?

No hard and fast rules can help you predict how long your wheel speed sensor will last. It depends on the car you own and the way you maintain it. There are external factors that impact the sensors. But generally, the speed sensors last about 50,000 miles.

Can A Defective Speed Sensor Cause A Rough Idle?

A faulty speed sensor can cause a vehicle to idle erratically and consume more fuel than necessary.  It results in sluggish acceleration and other engine problems. This is due to incorrect signals from the speed sensor area to the fuel system.

The most common speed sensor symptoms are rough idling at low speeds or when accelerating out of traffic lights. If you notice any unusual behavior in your car while driving, it may be time for an inspection.

Cost Of Replacing Speed Sensors

The price may differ depending on the type of vehicle you own. You may have to pay around $250 for a Kia or a Nissan sedan. Parts would cost around $150, with the remainder being labor costs. For more expensive cars, such as a Porsche 911, it can cost around $425, with parts costing $230 and labor about $195.

The cost also depends on the total amount of work involved, including other related issues.


After some time behind the wheel, you may begin to notice speed sensor symptoms as given in this article. It is important to understand all bad speed sensor symptoms so that you can take immediate action to resolve the problem.

If your car’s speed sensor begins to emit a check engine light or if the speedometer stops working, you may have a problem. If you notice any of the symptoms described above, you should have them checked right away. Timely action will ensure that your vehicle isn’t suffering from more serious damage.

Driving with a faulty speed sensor could be extremely dangerous. It could cause considerable damage to your vehicle and even lead to an accident. If you notice any of the speed sensor symptoms, you must have it repaired as soon as possible.

You surely would not want to wait until something goes wrong to figure out what caused it. Use this article as a guide for identifying the issue and then resolving it.

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