Vehicle Speed Sensor: Description and Operation

How the Circuit Works
With the ignition switch in ON (II) or START (III), battery voltage is supplied through fuse 15 and the BLK/YEL wire to the vehicle speed sensor (VSS). The sensor is grounded by the BLK wire to G101 The speedometer and other control units in the circuit supply about 5 volts to the ORN wire. The vehicle speed sensor (VSS) intermittently grounds the ORN wire which generates a pulsed signal in it. The number of pulses per minute increases/decreases with the speed of the car.