Fuel Tank Vapor Pressure Sensor

The fuel tank pressure sensor is used to detect small leaks in the evaporative emission system. The fuel tank pressure sensor is a three wire strain gauge sensor much like that of the common GM 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. The sensor mounts at the top of the fuel tank. A three wire electrical harness connects it to the Powertrain Control Module (PCM). The PCM supplies a five volt reference voltage and 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 be 1.3 to 1.7 volts. Refer to [1][2]EVAP Control System Diagnosis.