What is the Speed Sensor all about?

Located on the transmission case, within the rear differential assembly or inside the ABS system, the vehicle speed sensor reads the speed of the wheel rotation on a vehicle while driving. The sensor also helps the vehicle maintain stability while driving by telling the computer when to release pressure to a wheel while using the ABS. A type of tachometer, the part consists of a toothed ring and pickup. The speed sensor reads the rotational speed of the reluctor wheel, located within the transmission. Speed sensors within the differential use a trigger wheel mounted in conjunction with the ring gear to accomplish the same tasks as those performed by the transmission-mounted version.

Keep in mind:

• The mechanic will run a diagnostic on the vehicle to find the exact cause of the problem.
• A faulty speed sensor sometimes produces symptoms similar to a failing transmission.
• The mechanic will check the transmission.
• Some vehicles use the information from the sensor to help determine ride height, a feature in newer vehicles.
• The mechanic will check all connections to make sure everything remains connected properly.

How it's done:

• The speed sensor is verified that it needs to be replaced. The vehicle is lifted and supported on jack stands.
• The speed sensor is located in the rear axle. The speed sensor is removed from the rear axle housing.
• The new speed sensor is installed into the axle housing.
• The speed sensor connector is connected. The vehicle is removed from the jack stands.
• The vehicle is road tested and scanned for proper operation of the speed sensor.

Our recommendation:

When replacing the vehicle speed sensor, the mechanic will first run a diagnostic to make sure that the problem does not lie with the transmission instead. Replace a faulty speed sensor as soon as possible to avoid further damages on your vehicle. The speed sensor also controls the anti-lock braking system. Driving with a bad speed sensor usually causes the ABS to malfunction and can lead to loss of braking power and/or an accident. The speed sensor likewise affects the transmission, causing it to perform erratically.

What common symptoms indicate you may need to replace the Speed Sensor?

• Odometer does not work
• Speedometer stops working or performs erratically
• Cruise control fails to function properly
• Transmission hesitates to shift gears or shifts roughly, sometimes revving higher as the driver shifts gears
• Transmission jumps gears
• Vehicle idles incorrectly
• Vehicle rumbles
• Vehicle suddenly loses power
• Fuel efficiency drops
• Check Engine Light, brake, or anti-lock warning lamps come on

How important is this service?

While vehicle owners can get away with not replacing a vehicle speed sensor initially, they can expect the vehicle’s usability to only worsen over time. Owners want to refrain from waiting until the part goes out completely, which could cause critical vehicle systems, such as the speedometer and anti-lock brakes, to stop functioning entirely.