Many modern vehicles have a speed sensor. This sophisticated component is used to detect the speed of the vehicle and pass this information on to a variety of other components such as the anti-lock braking system, the cruise control system and the variable assist power steering system.
The majority of newer vehicles with a speed sensor will have a model that operates through a permanent magnet. The speed sensor will be mounted either in the vehicle’s rear differential assembly or in the transmission case. If the speed sensor is mounted in the transmission case it is most likely that it will be gear driven whilst a speed sensor mounted in the rear differential operates by means of a trigger wheel that is mounted with the ring gear. Regardless of the location of the speed sensor mounting, the same information is collated and distributed electronically to other parts of the vehicle.
Because there are several tasks to which the speed sensor is integral, a faulty sensor might reveal itself in a variety of ways. If the cruise control stops working, the speedometer ceases to operate or the anti lock braking system begins to behave erratically, the source of the problem may well be a faulty speed sensor.
If this is the case it is essential to replace the faulty sensor to ensure that the functioning of all of those dependent components is restored.