Analog Instrument Panels: Operation: Tachometer

The tachometer gives an indication to the vehicle operator of the engine speed. This gauge is controlled by the electronic circuit board based upon cluster programming and electronic messages received by the cluster from the PCM over the PCI data bus. The tachometer 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 electronic circuitry controls the gauge needle position and provides the following reasons: engine speed message, message failure, and actuator test.