Tachometer: Description and Operation

Voltage is applied to the tachometer from the gauge fuse, located in junction block 2, when the ignition is in the ON or START positions. Current flows from the gauge fuse to junction block 3, via the RED/BLU wire between the junction block 2, C2 cavity 9 and the junction block 3, C3 cavity 5. Current flows to the instrument cluster assembly C1 cavity 2 from the junction block 3, C2 cavity 18.

The tachometer displays engine speed in revolutions per minute (RPM). Engine RPM data is received from the PCM through the BLK wire between the PCM C3 cavity 8 to the instrument cluster assembly C3 cavity 3, after going through SP258. The tachometer responds to the frequency of the pulses the PCM send it, when the pulses increase the tachometer increases.