Instrument Cluster Description and Operation: Tachometer

The engine control module (ECM) sends the engine speed to the instrument panel module (IPM) via GMLAN. The instrument panel cluster (IPC) displays the engine speed as determined by the IPM. The IPC receives a GMLAN message from the IPM indicating the engine speed. The tachometer will default to zero if:

• The ECM detects a malfunction in the engine speed signal.
• The IPC detects a loss of GMLAN communications with the IPM.
• The IPM detects a loss of GMLAN communications with the ECM.