In order for a driver to be able to keep track of the speed at which a vehicle is travelling the speedometer system displays it in analogue or digital form in a display on the dashboard. The way in which the speedometer display is able to show the reading is though the receipt and translation, by the vehicle’s computer, of electric signals that are sent by the speedo sensor.

The speedo sensor is attached to the vehicle’s crankshaft and makes an assessment of how quickly it is spinning. When the crankshaft turns, an electric current is created around a magnetic coil which, in combination with a serrated metal disc, produces a magnetic field. It is this magnetic field that provides the measurement of the electrical current that is produced and this, in turn, is displayed as the speed of the vehicle.

There are various indicators of a faulty speedo sensor. The most obvious signs that the speedo sensor has failed are problems with the operation of the cruise control and the failure of the speedometer display to show the vehicle’s speed.

Any problems with the speedo sensor should be dealt with quickly. The problem may lie in the electric connections within the system. If the issue rests with the speedo sensor itself, a replacement part should be fitted.