Instrument Cluster Description and Operation: Tachometer

The instrument cluster displays the engine speed based on the information from the ECM. The ECM converts the data from the crankshaft position sensor to an engine revolution signal. The ECM sends the engine speed information via a engine speed signal circuit to the instrument cluster to display the engine speed.

In some vehicle/option configurations, the discreet engine speed signal circuit is present, but not used for tachometer operation. In these configurations, the Engine Control Module sends engine speed information to the Instrument Cluster via serial data. The Instrument Cluster then uses the serial data messages for tachometer operation.