Instrument Cluster Description and Operation: Tachometer

The instrument panel cluster (IPC) displays the engine speed as determined by the engine control module (ECM). The engine control module (ECM) determines the engine speed and sends the engine speed serial data message to the BCM. The BCM sends the engine speed via the serial data circuit to the IPC. The tachometer will default to 0 RPM if:

• The ECM detects a malfunction in the engine speed sensor.
• The BCM detects a loss of serial data communication with the ECM.
• The IPC detects a loss of serial data communication with the BCM.