Speedometer Head: Description and Operation

When the ignition switch is in ON (II) or START (III), battery voltage is supplied through fuse 1 to the gauges in the gauge assembly. The gauge circuit is grounded at G404.

The odometer and speedometer drive circuits receive pulses from the vehicle speed sensor (VSS) or powertrain control module (PCM). The pulse rate increases as the car accelerates. The frequency and duration of these input pulses are measured and displayed by the speedometer, odometer and tripmeter.