Symptoms of a Faulty Speed Sensor and Replacement Instructions

Vehicle speed sensors are used to sensor input for the traction control and the anti-lock brake system (ABS) on vehicles equipped with computerized systems. The vehicle speed sensor sends data to the transmission to control gear shifts. The vehicle also uses the data collected from the speed sensor for the cruise control if it is installed in the car, the ABS system, and many other essential functions. Vehicle speed sensors come in many different designs depending upon the type of vehicle that they are intended for. Occasionally, a speed sensor can go bad and will need to be replaced. Speed sensor replacement is an auto repair job that is considered part of regular maintenance and is fairly easy to do.

What Does a Speed Sensor Do?

A speed sensor is a magnetic coil that is plugged into the transmission on most vehicles. It is used to monitor the speed of the vehicle and the transmission gears. It then sends this information to the speedometer on the dashboard to let the driver know how fast they are going. Speed sensors are typically driven by a gear that is located on the output shaft. As the shaft of the sensor spins, it generates a signal that it sends to other parts of the vehicle’s computer system such as the powertrain computer module (PCM) and the transmission computer module (TCM). The PCM then uses this signal to determine the speed of the vehicle.

Where is the Speed Sensor Located?

Most speed sensors are located on the transmission case or the rear axle of the vehicle. However, some later model vehicles have them inside the ABS system. When looking for a speed sensor. If it cannot be seen on the transaxle, it is probably inside the ABS module. As most speed sensors are located on the transmission case, this is the first place that should be checked.

What are the Symptoms of a Faulty Speed Sensor?

One of the most noticeable symptoms of a faulty speed sensor is the odometer or speedometer of the vehicle not working. In some cases, if the speed sensor is damaged, cruise control will also not work. Symptoms may also present themselves within the transmission, and the vehicle may be rough or hesitate when trying to shift gears. The transmission may also jump gears. Some other symptoms can include the vehicle rumbling or not idling correctly. It may also burn more fuel than usual, and it may suddenly lose power.

What Steps Need to be Taken to Replace the Speed Sensor?

Once the speed sensor has been located, it is time to collect some tools and begin the replacement repair. To do this, a jack, jack stands, and an open-ended wrench will be needed. The vehicle will first need to be jacked up and placed onto jack stands. It is very important to ensure that the vehicle is secure and will not fall while the mechanic is underneath it performing the repairs. Next, located the speed sensor underneath the vehicle, it looks a little like a small plug that sticks out of the transmission with another plug connected to it. Squeeze the release tab on the top of the electrical plug and remove it. Then remove the sensor by using the wrench to turn it counterclockwise. Once the speed sensor is removed, install the new one by screwing it in clockwise. Once the new speed sensor is installed, the car can be lowered and taken off the jack stands. The new speed sensor can then be tested.

If a vehicle is experiencing any of the symptoms of a faulty speed sensor, it should be taken to a mechanic so that they can run a full computer diagnostic on the vehicle. In many cases, a faulty speed sensor will produce symptoms in the transmission and make an auto repair specialist believe that the transmission is going bad. This is why it is best to have a computer diagnostic test ran to ensure that the correct maintenance and repairs are done. The mechanic will then recommend a replacement of the speed sensor, and then you will be well on your way to a well-running vehicle.