Circuit Operation

With the ignition switch in RUN or START, battery voltage is supplied through fuse 22 to the vehicle speed sensor. 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 in the circuit. The vehicle speed sensor pulses the YEL/RED wire by grounding it. The number of pulses per minute varies with the vehicle speed.