Speedometer Head: Description and Operation

SPEEDOMETER

The IPC displays the vehicle speed on the analog speedometer based on the vehicle speed signal from the PCM. The PCM converts the data from the vehicle speed sensor to a 4,000 pulses/mile signal. The IPC uses the vehicle speed signal circuit from the PCM in order to calculate the vehicle speed.

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