Fuel Pump Signal: Description and Operation

PURPOSE
The Fuel Pump Monitor (FPM) circuit is spliced into the Power-To-Pump circuit and is used by the PCM for diagnostic purposes.


OPERATION
The PCM sources a low current voltage down the FPM circuit. With the fuel pump Off, this voltage is pulled low by the path to ground through the fuel pump. With the fuel pump Off and the FPM circuit low, the PCM can verify that the FPM circuit and the Power-To-Pump circuit are complete from the FPM splice through the fuel pump to ground.

This also confirms that the Power-To-Pump or FPM circuits are not shorted to power. With the fuel pump On, voltage is now being supplied from the Fuel Pump Relay to the Power-To-Pump and FPM circuits. With the fuel pump on and the FPM circuit high, the PCM can verify that the Power-To-Pump circuit from the Fuel Pump Relay to the FPM splice is complete. It can also verify that the fuel pump relay contacts are closed and there is a B+ supply to the Fuel Pump Relay.