Vehicle Speed Sensor (VSS)

The vehicle speed sensor (VSS) is mounted to the transmission and produces an AC signal. The frequency of this signal is proportional to the speed at which the transmission output shaft rotates, which in turn, is proportional to the speed of the vehicle. The AC signal produced by the vehicle speed sensor (VSS) is amplified and converted by the vehicle speed sensor (VSS) buffer.

The signal is supplied the ECM, cruise control module, and speedometer by the vehicle speed sensor (VSS) buffer. The vehicle speed sensor (VSS) buffer produces the signal by opening and closing internal solid state switches to ground. The signal to the ECM is at a rate of 2,000 pulses per mile while the cruise control module and speedometer see a rate of 4,000 pulses per mile. The ECM cruise control module, and speedometer internally convert the number of pulses per mile per second to determine vehicle speed.