Fuel Tank Pressure Sensor

The Fuel Tank Pressure (FTP) sensor measures the difference between the air pressure, or vacuum, in the fuel tank and the outside air pressure. The sensor mounts at the top of the fuel sender assembly. See Figure . The PCM supplies a 5-volt reference voltage and ground to the sensor. The sensor provides a signal voltage between 0.1-4.9 volts to the PCM. When the air pressure in the fuel tank is equal to the outside air pressure, such as when the fuel fill cap is removed, the output voltage of the sensor will measure 1.3-1.7 volts. When the air pressure in the tank is 4.5 in. H2O, the sensor output voltage should measure 0.3-0.7 volt. The sensor voltage increases to approximately 4.5 volts at 14 in. H2O. As the FTP increases, FTP sensor voltage decreases, high pressure = low voltage. As the FTP decreases, FTP voltage increases, low pressure or vacuum = high voltage.