What Happens When A Speed Sensor Goes Bad?


Speeding is the most common and perilous driving habit of drivers. Almost one-third of fatal accidents occur due to speeding. However, keeping an eye on the speed sensor measuring your speed on the road is one way to keep the passengers safe. Not many of us might have realized the importance of the feature added to the vehicle that helps you drive properly. Over time you may notice problems such as bad speed sensors in a car, and driving with it becomes a matter of life and death. Speed sensor replacement would fix these issues in no time.

What is a Speed Sensor & Its Functioning?


A speed sensor is a tiny car component mounted on its transmission and provides speed information to your car’s overboard computer. Many people call it a wheel speed sensor, transmission speed sensor, or output shaft speed sensor.

The speed sensors calibrate the rotational speed of the gears present in the transmission system. The results obtained from it are converted into analog signals or a low voltage square wave signal and delivered to the ECU located within your car. Even the vehicle’s cruise system depends on the readings given by the speed sensor, and it is impossible to maintain a constant speed of the car.

Symptoms of a Bad Speed Sensor


Below is the list of bad speed sensor symptoms which indicates an issue:

Odd Speedometer Readings

Most cars rely on speed sensors to manage their speedometer readings. Issues with the sensor lead to inaccurate readings, or the readings won’t come at all. However, it won’t stop the working of the car. You won’t be able to get the idea of how fast the car works, and driving a vehicle in such situations can put your life at risk. It is better to get the car inspection from the mechanic for a speed sensor replacement in such scenarios.

Check Engine Light On

Various reasons can be held liable for an illuminating check engine light:

  1. A faulty ignition coil or spark plug.
  2. Issues with the fuel injector.
  3. Poorly performing thermostat.

It is impossible to detect the transmission speed of a sensor signal in such situations. The electronic control unit shows errors and illuminates the car engine light. Delaying the issue won’t make it better, so taking the car for a mechanic inspection is better.

Malfunctioning Cruise Control

A car’s cruise control system relies on the input it gets from the transmission speed sensor. In the case of a problematic speed sensor, it is impossible to get the desired performance from the car’s cruise control. Driving with problematic cruise control can be a hassle, so it is better to call the mechanic who will fix the issues in no time.

Issues in Transmission Shifting

Without a proper signal from the transmission speed sensor, it is impossible to shift the gears of the transmission system. As a result, PCM starts producing rough gears and impedes the timing of your transmission shifts. If your car works on an automatic transmission system, a faulty sensor severely damages the transmission gear tooth profile. To be on the safe side, try to fix the transmission yourself, but before that don’t forget to determine the speed sensor cost.

How Often Should the Speed Sensor Be Replaced?

It is difficult to determine the longevity of the speed sensor. Like other car parts, it is supposed to last for a lifetime. The transmission speed sensor generally lasts between 30,000 to 50,000 miles. The lifespan of your speed sensor depends on how you drive?

Continuous exposure won’t make these components last.

The lifespan of the speed sensor reduces in the following situations:

  • Poorly installed speed sensor.
  • Electrical faults in the speed sensor lighting.
  • Damages on the tone ring.
  • Defects found in magnetic speed sensor or inductive sensor coil.
  • The speed sensor tip is filled with contaminants.
  • The connection between the transmission speed sensor and electronic control unit is lost.
  • Vehicle not maintained properly.

How Much Does a Speed Sensor Replacement Cost?

The average cost of replacing a speed sensor lies between $150-$200.Labor charges and the cost of the parts are charged separately. If you think that the sensor replacement is going over budget, buy the part from the best online store, ‘The Auto Parts Shop,’ and fix the issue on your own.

The Bottom Line

Prevent speeding issues by replacing a bad speed sensor. However, not doing so can lead to bigger problems, so find the solution today.

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