Circuit Operation

The Vehicle Speed Sensor (VSS) is a gear-driven Permanent Magnet Generator housed in the vehicle's Transaxle. This sensor generates a sine wave output with a frequency proportional to vehicle speed. The Powertrain Control Module (PCM) converts this signal to an output that is switched to ground at a frequency of 4000 pulses per mile at the CKT 389 output. This output is pulled up to 5 volts or greater by the components that use this speed signal as an input.