Tachometer: Description and Operation

The tachometer displays engine speed in rpm. Voltage pulses are taken from the ignition system and sent to the tachometer. The tachometer responds to the frequency of the voltage pulses which vary according to engine speed. ECM process these pulses into a signal that causes the gauge needle to move.

When the fuel level is below the thermistor, the resistance of thermistor varies, providing a ground for the low fuel indicator bulb.