Speed sensors are part of a vehicle's anti-lock braking system (ABS). The speed sensors are designed to convey data regarding the speed of the vehicle to the in-car ABS computer system. The sensors are magnetic, and this makes them attract dust and debris. The various components of the speed sensors can gather dirt from the road and from the dust that is generated by constant sharp braking. Speed sensors need to be cleaned on a regular basis to avoid damaging the anti-lock braking system.
Prepare the area by gathering all materials and placing them within reach. If you need to wear overalls and a face mask to protect from dust, do so at this point.
Lift up the front of the car, and place it on the jack stands. Place wheel blocks around the rear wheels. Take the lug wrench, and remove the wheel by unscrewing each nut. Place the wheel in a safe place.
Locate the sensor, and decide whether it is an open or disguised sensor. Look for the reference ring; if you can see it to the rear of the brake rotor, then this is an open sensor. Hidden or disguised sensors can be located within the differential housing. This type of sensor does not require regular cleaning or maintenance, as they are hidden away from excess dirt and dust.
Take the wrench, and unfasten the sensor. Detach it from the bracket carefully. Pay particular attention to the wires surrounding the housing, as carelessness could cause damage to the wires.
Spray the rag with degreaser. Clean the sensor gently, paying careful attention to the top of the sensor, as this is the most sensitive part.
Spray the brush with degreaser solution, and carefully remove any dirt from the reference ring. Thoroughly clean in between the holes and crevices of the reference ring, until it is free of debris.
Place the sensor back in the housing bracket, and put the wheel back. Secure the wheel using the wrench. Each sensor will have to be cleaned; clean the sensor on the other front wheel.
Lower the vehicle and remove the jacks, make sure that all the wheels have been replaced securely.
Repeat the process on the rear wheel sensors.
If the anti-lock brake system has been having problems, due to the dirt on the sensors, take the car for a 10-minute drive to make sure that the sensors are working correctly. If they are still causing problems, take the car to a specialist to identify the problem.