TSB : ELECTRA, LESABRE & Park Avenue Instrument Panel: Speedometer

Details

The Vehicle Speed Sensor (VSS) is a driveshaft driven magnetic pick-up. The VSS coil produces an alternating current. The faster the driveshaft turns, the higher the frequency induced in VSS coil. This voltage is sent to the solid-state vehicle speed sensor buffer. The buffer converts the alternating current into pulses. The pulse rate reflects vehicle speed and is compared to a reference voltage at speedometer. The difference between reference voltage and pulse rate causes the speedometer needle to deflect. Needle deflection indicates vehicle speed.