Escort L4-121 2.0L SOHC VIN P SFI (2002)
Vehicle Speed Sensor: Description and Operation
PCM Input
Vehicle Speed Sensor
Typical Vehicle Speed Sensor (VSS)
The Vehicle Speed Sensor (VSS) (Figure 44) is a variable reluctance or Hall-effect sensor that generates a waveform with a frequency that is
proportional to the speed of the vehicle. If the vehicle is moving at a relatively low velocity, the sensor produces a signal with a low frequency. As the
vehicle velocity increases, the sensor generates a signal with a higher frequency. The PCM uses the frequency signal generated by the VSS (and other
inputs) to control such parameters as fuel injection, ignition control, transmission/transaxle shift scheduling and torque converter clutch scheduling.
