Analog Instrument Panels: Operation: Speedometer

The speedometer gives an indication to the vehicle operator of the vehicle road speed. This gauge is controlled by the instrument cluster electronic circuit board based upon cluster programming and electronic messages received by the cluster from the PCM over the PCI data bus. The speedometer is an air core magnetic unit that receives battery current on the instrument cluster electronic circuit board through the fused ignition switch output (run-start) circuit whenever the ignition switch is in the ON or START positions. The cluster is programmed to move the gauge needle back to the low end of the scale after the ignition switch is turned to the OFF position. The instrument cluster circuitry controls the gauge needle position and provides the following features: vehicle speed message, message failure, and actuator test.