Fuel Temperature Sensor: Description and Operation
Bi-Fuel/Alternative FuelsFUEL TEMPERATURE SENSOR (FTS)
The FTS is a thermistor mounted inside the HPL and is not serviceable separately from the HPL. The FTS thermistor has high resistance when cold and low resistance when hot. The AF ECU supplies about 5 volts to the FTS signal circuit. When FTS resistance is high (cold sensor) the FTS signal voltage is high. As the FTS warms and resistance drops, less signal voltage is monitored by the AF ECU. The volume of CNG varies with temperature and pressure. This will vary the amount of fuel vs. the signal voltage the FPS supplies to the AF ECU. In order to compensate for the different voltage factors, the tank mounted (internal) fuel temperature sensor (FTS) is monitored by the AF ECU. The AF ECU performs a calculation on the FPS voltage vs. the in-tank temperature. The AF ECU will then control the fuel gauge to display the correct fuel level.