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 Fuel Tank Pressure Sensor (1) is mounted on top of the modular fuel sender. The sensor measures the difference between the fuel vapor pressure (or vacuum) in the fuel tank and the outside air pressure. A three wire electrical harness connects it to the Powertrain Control Module (PCM). The PCM supplies a 5 volt reference signal and ground to the sensor The sensor will return a voltage between 0.1 volts and 4.9 volts back to the PCM depending on the fuel vapor pressure in the fuel tank. When the fuel pressure in the fuel tank is equal to the outside air pressure, such as when the fuel cap is removed, the output voltage will be 1.3 volts to 1.7 volts.

When the air pressure in the tank is 4.5 inches H2O (1.25 kPa), the sensor output voltage should measure 0.5 plus/minus 0.2 volts. When there is neither a vacuum or a pressure in the tank, the sensor voltage should be at 1.5 volts at 14 inches H2O (-3.75 kPa) the sensor output voltage should be 4.5 volts plus/minus 0.2 volts.

Refer to System Diagnosis / Diagnostic Tables for testing information. Testing and Inspection