Fuel Tank Pressure (FTP) Sensor

The FTP sensor is a pressure transducer. The AF ECM supplies about 5 volts on the FTP reference circuit. The AF ECM also supplies a signal and ground circuit to the FTP. Located at the front fuel tank, threaded into the HPL, the FTP supplies a voltage signal to the AF ECM. With the fuel tanks full (high pressure) a high voltage signal will be monitored by the AF ECM.

The volume of CNG will vary with temperature and pressure. This will vary the amount of fuel vs. the signal voltage the FTP supplies to the AF ECM. In order to compensate for the different volume factors, an HPL mounted (internal to the tank) Fuel Tank Temperature (FTT) sensor is also monitored by the AF ECM. The AF ECM performs a calculation on the FTP voltage vs. the in-tank temperature. The AF ECM will then control the fuel gauge to display the correct fuel level.

The CNG FTP sensor should not be confused with the GASOLINE Fuel Tank Pressure (FTP) sensor that is utilized for Evaporate (EVAP) emissions monitoring.