Fuel Tank Pressure Sensor: Description and Operation

DESCRIPTION
The Fuel Pressure sensor is a three wire strain gauge sensor much like that of the common Manifold Absolute Pressure (MAP) sensor. However, this sensor has very different electrical characteristics due to its pressure differential design. The sensor measures the difference between the air pressure (or vacuum) in the fuel tank and the outside air pressure.

PURPOSE
The sensor mounts at the top of the fuel tank sending unit. A three wire electrical harness connects it to the PCM. The PCM supplies a 5 volt reference voltage and a ground to the sensor. The sensor will return a voltage between 0.1 and 4.9 volts.

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 measures 1.3 to 1.7 volts.