Fuel Tank Temperature (FTT) Sensor

The FTT is a thermistor mounted inside the HPL and is not serviceable separately from the HPL.

The FTT thermistor has high resistance when cold and low resistance when hot. The AF ECM supplies about 5 volts to the FTT signal circuit. When FTT resistance is high (cold sensor) the FTT signal voltage is high. As the FTT warms and resistance drops, less signal voltage is 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.

Only the fuel tank temperature sensor of the front tank HPL is monitored by the AF ECM.