Fuel Tank Pressure Sensor
WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.
The Fuel Tank Pressure (FTP) sensor, measures the difference between the fuel tank and outside air pressure. The PCM provides a 5-volt reference and a ground to the FTP sensor. The FTP sensor provides a signal voltage back to the PCM that can vary between 0.1 and 4.9 volts. As the fuel tank pressure increases, FTP sensor voltage decreases, as the fuel tank pressure decreases, FTP sensor voltage increases. High pressure equals high voltage. Low pressure vacuum equals low voltage.