Fuel Tank Pressure Sensor (CNG): Description and Operation

FUEL TANK PRESSURE (FTP) SENSOR

The FTP sensor is a pressure transducer. The fuel injector control module (FICM) supplies about 5 volts on the FTP reference circuit. The FICM also supplies a signal and ground circuit to the FTP. When the fuel tanks are full (high pressure) a high voltage signal will be monitored by the FICM. The FTP sensor is threaded into the fuel tank HPL solenoid. The FTP sensor voltage is sent to the PCM through a PWM circuit. The volume of CNG will vary with temperature and pressure. Accurate CNG fuel level cannot be determined by pressure only. In order to compensate for the different volume factors a fuel tank temperature (FTT) sensor is mounted within the HPL. The PCM performs a calculation on the fuel tank pressure vs. the in-tank temperature. The PCM will then display the temperature corrected CNG 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.