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 engine speed sensor to an engine revolution signal. The ECM sends the engine speed information via a High Speed CAN-Bus signal to the BCM. The BCM then sends the information via a Low Speed CAN-Bus signal to the instrument cluster to display the engine speed. The tachometer defaults to 0 RPM if:

• The ECM detects a malfunction in the engine speed sensor circuit.
• The BCM detects a loss of serial data communications with the ECM.
• The instrument cluster detects a loss of serial data communications with the BCM.