The control module monitors the fuel tank pressure (FTP) sensor signal in order to detect vacuum decay and excess vacuum during the enhanced evaporative emission (EVAP) diagnostic. The Fuel Tank Pressure Sensor responds to changes in the fuel tank pressure or vacuum. This information is used in order to detect vacuum decay or an excessive vacuum during EVAP diagnostic routing. The fuel tank pressure sensor signal voltage to the VCM varies from a minimum of about 0.1 volts with pressure in the fuel tank to above 4.0 volts with a high vacuum in the fuel tank.
The following schematic shows the Typical Fuel Tank Pressure Sensor Circuit Diagram.