Bad Speed Sensor Symptoms (Causes & Fix)

Some drivers may overlook the bad speed sensor symptoms. However, speed sensor problems may be encountered when driving. For example, the anti-lock braking systems and traction control light may show up suddenly, or the vehicle may start being sluggish for unknown reasons.

These lights shut out without any external influence. However, they usually appear again after a very short time. The vehicle’s transmission may also look like it can not go above and below a particular speed, which will prevent the vehicle from speeding up.

These are bad speed sensor symptoms, and in this article, speed sensors will be examined, including what it is and how it works, signs that show up when there is a problem with them, as well as how these problems can be properly fixed.

Bad Speed Sensor Symptoms

Bad Speed Sensor Symptoms

1. Difficulty in Changing Gears

Difficulty changing gears is a common bad speed sensor symptom.

If it becomes a little difficult to change gears in a vehicle, this could indicate that something has gone wrong with the sensors. The role of the sensor is to convert the rotation of the transmission to the voltage on signal cables in correspondence to the engine’s speed.

Then the converted signal is sent to flywheel input shafts through various gears, which put the clutch discs to work. A few slippages may occur between the components mentioned above if worn or damaged.

A few times, speed sensors may become wet or dirty, and this would cause transmission problems.

2. Speedometer Not Working

A non-functioning speedometer is a common bad speed sensor symptom. A vehicle’s speedometer shows that the vehicle is moving at speed faster than the real speed of the vehicle. For example, a speedometer’s needle may be fixed at 40mph; however, the vehicle is stationary and not moving. These are signs that a vehicle’s speed sensor is faulty.

A faulty speed sensor can give the vehicle wrong speed readings, resulting in drivers making poor driving decisions.

The problem could be that the sensor transmits inaccurate readings to the Electronic Control Unit, or the speed sensor cannot transmit any signal to the electronic control unit. There may also be the need to change speed sensor cables, which means new cables will be bought.

3. Check Engine Light Turns On

A common bad speed sensor symptom is the illumination of the check engine light.

If the check engine indicator should come on, this could mean there is an issue with the vehicle’s speed sensor. A speed sensor acts as a tool for measuring the speed of a vehicle.

When it cannot do this or develops a problem with sending signals, it can cause the vehicle to idle inconsistently, or the vehicle’s power output may become low. As a result, a vehicle may not be able to maintain a cruising speed.

If an object gets in the way of the alarm system of a vehicle, it may also trigger the check engine indicator to come on.

4. Cruise Control Not Engaging

If a vehicle cannot engage in cruise control, this could be due to a problem with the speed sensor. Cruise control is what makes a vehicle maintain a particular speed. Some speed sensors can detect when the vehicle’s speed changes. This aids the cruise control in fixing a particular speed for the vehicle.

Speed sensors measure tire rotation, and then the information is transferred to the Electronic Control Unit. A vehicle may fail to activate cruise control at times.

Speed sensors inform the cruise control on how quickly it should move and when it should slow down. If there’s a fault with this sensor, the vehicle may speed up constantly or become stationary.

5. Torque Converter Clutch Issue

Another bad speed sensor symptom to look out for is problems with the torque converter clutch.

The speed sensors of a vehicle trigger the torque converter clutch when the vehicle’s speed hits a point that has been established earlier. Although, these sensors will not be able to send the torque converter to the clutch, which is very important for the vehicle.

The torque converter and clutch will not be able to create a smooth and good working relationship. Slipping, reduced fuel economy, and the transmission becoming too hot can all happen due to this problem.

The anti-lock braking system indicator occurs when a vehicle’s speed sensor is faulty. Unfortunately, this means there is no way the vehicle will know its exact speed (i.e., how slow or fast it is moving.); hence the brakes won’t work properly.

The anti-lock braking system light shows a problem with the speed sensor. As stated, speed sensors measure wheel rotation, after which it transmits the data to other sections of the vehicle’s electronics, which further transmit to the ECM. Therefore, a damaged speed sensor cannot give accurate signals to other electronic components of the vehicle.

6. Stability Control Light On

The stability control indicator comes on when a speed sensor is faulty. Although an electronics problem, it may, however, come on due to a problem with the speed sensor. A stability or traction control light shows that a speed sensor is faulty.

The stability or traction control indicator will come on when the vehicle’s engine hits a particular rotation per minute (RPM) due to a malfunctioning speed sensor.

7. Sluggish Acceleration

Engine computers may receive inaccurate signals due to damaged speed sensors. The speed sensors inform a vehicle’s computer how high the vehicle’s speed should be.

In a situation where this sensor fails to work, the vehicle will be unable to detect when to increase acceleration, which will make the vehicle slow.

Also Read: Wheel Speed Sensor Location (How to Locate the Wheel Speed Sensor)

What Is a Speed Sensor, and What Does It Do?

Bad Speed Sensor Symptoms

As mentioned earlier, speed sensors (also called the VSS or vehicle speed sensor) determine the speed at which the vehicle moves. The vehicle’s speedometer is not the only component that benefits from the speed sensor because some other components need the speed sensor, which is very important to them.

For vehicles equipped with automatic transmission, as we have them a lot in these times, speed sensors aid the vehicle’s computers in charge of changing gears to make sure the shifting occurs when it should.

Furthermore, suppose a vehicle has a cruise control facility. In that case, the cruise control’s function is also aided by the speed sensors, which help ensure that the vehicle’s speed remains consistent.

Speed sensors are usually connected to the vehicle’s transmission, and their function is to measure the rotational speed of the gears within. The speed sensor then transmits the data to different control units of the vehicle. In turn, they use this data supplied to regulate other areas in the vehicle’s overall performance.

How to Replace Your Car’s Speed Sensor

Although vehicle owners can change the speed sensor of their vehicles on their own, it is highly recommended that the vehicle be taken to a workshop where it can be properly done.

A few safety equipment and tools may be needed to change speed sensors properly, and unless these equipment are readily available, it will most likely cost some money to buy all of this equipment.

Furthermore, if the required experience to undertake a repair like this is unavailable, it may be a challenging task to execute.

However, if the practical experience, as well as the required tools, are available, then this procedure can help in properly replacing the speed sensors of a vehicle:

  1. Jack up the vehicle and keep it in the jacked position using a jack stand. Afterward, go under the car where the speed sensor is fixed to the transmission.
  2. Put a container under the speed sensor to gather any transmission oil that may leak out when the speed sensor is removed.
  3. Take out the connector linking the speed sensor with the vehicle’s wiring. It might be required to loosen a tab to prevent the connector from breaking while removing it. Hence, it should be removed gently and not forcefully.
  4. After disconnecting the wirings successfully, a torque wrench can be used to take the old speed sensor away from the vehicle’s transmission.
  5. Fix the new vehicle speed sensor, then have it connected to the vehicle’s wiring.
  6. Finally, test drive the vehicle. If components that rely on the sensor like the speedometer, cruise control, and the transmission start working again, this could mean that the issue has been fixed. However, if they do not work, the best thing to do at this stage is to take the vehicle to a mechanic workshop for proper repairs.

Also Read: 10 Bad O2 Sensor Symptoms (Causes and Solutions)

What Causes the Speed Sensor to Fail?

Bad Speed Sensor Symptoms

1. An Internal Electrical Fault in the Speed Sensor

Internal damage to the speed sensor could cause the sensor to transmit no signal or abnormal signal. Generally, an oscilloscope or digital voltmeter can be used to test speed sensors.

Engage a professional mechanic to help in checking the vehicle if it is suspected that there is a fault with the speed sensors, so a test can be done and the sensors changed if necessary.

2. Damage to the Sensor Itself

A speed sensor can crack or get damaged. Also, a part of the speed sensor is made with plastic, and this portion may become soft after excessive exposure to heat and other elements.

The sensor’s metallic part may also get damaged and worn as time goes on.

3. Poor Vehicle Maintenance

Failure to adhere to the maintenance schedule of a vehicle increases the possibility of a speed sensor failure. This sensor cannot give accurate readings in a situation where the toothed wheel and/or magnetic pickup get covered in heavy gunk, especially contaminants from old transmission oil.

Is It Safe to Drive With a Failing Speed Sensor?

It is possible to run a vehicle with a damaged or faulty speed sensor, but it is not the best thing to do and is not encouraged. This is because a faulty speed sensor can negatively affect several aspects relating to a vehicle’s overall performance. This is why replacing a damaged speed sensor without delay is the best thing to do.

Suppose a vehicle owner notices any of the bad speed sensor symptoms, as stated above. Such a vehicle should be checked by a professional mechanic as soon as possible, or the vehicle owner can fix the issue immediately if he knows what should be done.

This will ensure the vehicles stay safe while being driven, and it helps prevent severe damage to the transmission and engine, which may occur with time. If a faulty speed sensor is not replaced, it may take a toll on the transmission and engine, as they will be denied the information they require for optimal performance.

These repairs come at a huge cost that may run into thousands or at least hundreds of dollars. Fixing them becomes more complicated, and the vehicle may need to be worked on for a more extended period than it ordinarily ought to take.

How Often Should You Replace the Vehicle Speed Sensor?

No straightforward rule can help predict the length of time a speed sensor will last.

Unlike brake calipers or brake light switches capable of lasting for a vehicle’s lifetime, a speed sensor is expected to last for about 30,000 to 50,000 miles.

Meanwhile, the driving conditions determine how long a brake pad speed sensor lasts. For example, if a vehicle’s speed sensor gets exposed to road salt and other elements, it will not last long.

Also, a speed sensor’s lifetime may be greatly reduced if exposed to the following conditions:

  1. If the speed sensors are wrongly installed.
  2. If the VSS wiring is faulty.
  3. If the tone ring is damaged.
  4. A less effective magnetic sensor or an inductive sensor coil
  5. Contamination of the VSS tip.
  6. If there is a disconnection between the ECU and the transmission sensor.
  7. If the vehicle is poorly maintained.

To avoid safety risks, if a symptom like a very high speedometer reading or if the cruise control starts to malfunction, get the VSS checked by a professional mechanic immediately and replace it, if necessary.

Bad Speed Sensor Symptoms

How Much Does a Speed Sensor Replacement Cost?

To replace speed sensors, the cost is determined by the brand and model of the vehicle. Another determinant is the kind of VSS in use, like a magnetic speed sensor(Hall effect speed sensor), an optical speed sensor, or any other type.

However, replacing speed sensors does not come at a huge cost. It is not as expensive as some other major repairs in a vehicle, such as replacing the master cylinder or brake line.

With the previous statements, around $225 to $380 should be enough to replace a VSS.

Also Read: Bad Knock Sensor Symptoms (+ Replacement Cost)

Frequently Asked Questions – Bad Speed Sensor Symptoms

What happens when a speed sensor goes bad?

If a speed sensor gets damaged and fails, it will directly affect the performance of the automatic transmission. A malfunctioning automatic transmission is a very common indication of a damaged speed sensor. If the speed sensor should develop a fault, the transmission system may start showing signs like restricted gear operation, hard shifts, and delayed shifts.

Can you drive with a bad speed sensor?

In the long run, the risk is not only limited to damaging the vehicle if driven with a broken WSS, but the driver’s safety is at risk too. If a driver thinks he has a broken speed sensor, it should be fixed immediately.

What happens if you unplug a speed sensor?

If you unplug the wheel sensors, such as the one working for the anti-lock braking system, the vehicle will work, but the anti-lock braking system will be unable to work effectively. On the other hand, if any of the engine sensors are disconnected, it is still possible for the engine to run. However, it will likely not run properly or trigger the check engine indicator.

Will a bad transmission speed sensor throw a code?

For a speed sensor to work properly, it relies on the information it gets from the transmission speed sensors. Therefore, if it does not work, then this means that the sensors are not working as they should. The PCM then transmits an error code to the electronic control unit, which will consequently shut down. If this happens, contacting a professional mechanic immediately to check the vehicle becomes a necessary option.

Can a speed sensor cause limp mode?

A damaged WSS can get a vehicle into limp mode. A bad WSS can result in the vehicle losing its stability and traction control. Consequently, this will trigger the Anti-lock braking system to disengage the stability and traction control systems. If its malfunction becomes consistent, the vehicle may go into limp mode.

Conclusion – Bad Speed Sensor Symptoms

Many issues can arise if a vehicle’s speed sensor is faulty. Indeed, a car that gives signs that its speed sensor has worn out can also trigger other connected symptoms in other areas of the vehicle, like a damaged coil pack or a malfunctioning throttle position sensor.

Symptoms of a damaged speed sensor have similar features that can cause problems for the vehicle’s engine and other components related to the engine.

Lastly, suppose any of the symptoms of a bad speed sensor stated above shows up. In that case, it is enough to make a vehicle owner visit a repair shop and have a qualified mechanic test the vehicle to properly identify the origin of the faults.

Although a few symptoms listed above may indicate a faulty transmission, the best thing to do is to have it checked with the best computer diagnostic equipment before visiting an auto repair shop specializing in vehicle speed sensors to confirm the real issues.

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