Fuel Tank Pressure Sensor

The fuel tank pressure sensor is a three wire sensor similar to the common 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 (vacuum) in the fuel tank and the outside air pressure.

The sensor mounts at the top of the fuel tank sending unit. A three wire electrical harness connects it to the ECM. The ECM supplies a 5 V reference voltage and ground to sensor. The sensor sends a voltage between 0.1 and 4.9 volts back to the ECM on its signal wire. 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 to 1.7 volts.