Instrument Panel Cluster (IPC) Description and Operation: Tachometer

The IPC displays the engine speed on the analog tachometer based on the engine speed signal from the PCM. The IPC uses the engine speed signal circuit - 2 pulses/engine revolution - from the PCM in order to calculate the engine speed.

The IPC also receives a class 2 message from the PCM indicating the engine speed. The IPC compares the class 2 value to the engine speed signal from the PCM to determine if the engine speed is valid. When the IPC detects a malfunction in the engine speed signal circuit, the IPC uses the class 2 message from the PCM to indicate the engine speed.