Fuel Tank Pressure Sensor: Description and Operation

Fuel Tank Pressure Sensor
The Fuel Tank Pressure Sensor is similar to the MAP sensor; however, the sensor is calibrated to different tolerances. The sensor measures the air pressure differences between the fuel tank and outside air.
The sensor uses a 5 volt reference voltage to send an output signal to the VCM. Depending upon the atmospheric pressure, the output voltage with the fuel cap removed will vary between 1.3-1.7 volts. A high voltage output (near 5 volts) indicates a very negative pressure (vacuum below - 4 kpa).