Fuel Tank Temperature Sensor (CNG)
WARNING: This page is about a different car, the 2002 Ford Pickup. However, it is still accessible from the selected car via links, so may be relevant.
Fuel Tank Temperature (FTT) sensor is a thermistor mounted on CNG fuel tank and is used along with Fuel Tank Pressure (FTP) sensor to calculate fuel density. Compuvalve sends FTT sensor a 5-volt reference signal. FTT sensor is also used to keep fuel gauge from fluctuating during temperature changes. If FTT sensor malfunctions, it will give a constant reading of 59°F (15°C).