Envoy 2WD V6-4.3L VIN W (1998)
Fuel Tank Pressure Sensor: Description and Operation
DESCRIPTION
The Fuel Tank Pressure sensor is a 3 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. The sensor mounts at the top of the fuel tank sending unit. A three wire electrical
harness connects it to the Control Module.
OPERATION
The Control Module supplies a 5 volt reference voltage and ground to the sensor. The sensor sends 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 measure 1.3
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 + 0.2 volts. The sensor voltage will be
approximately 1.5 volts when the fuel tank pressure is equalized with ambient pressure. The sensor voltage increases to approximately 4.5 volts at 14
inches of H2O (-3.75 kPa).
