Circuit Operation

With the ignition switch in RUN or START battery voltage is supplied through fuse 22 to the vehicle speed sensor (VSS). The sensor is grounded by the GRN/WHT wire through the powertrain control module (PCM). The YEL/RED wire is supplied about 5 volts by the speedometer and other control units that are in the circuit. The vehicle speed sensor (VSS) provides an intermittent ground which creates pulses in the YEL/RED wire. The number of pulses per minute varies with vehicle speed.