The fuel tank temperature sensor is used to detect the fuel temperature inside the fuel tank. The sensor modifies a voltage signal from the ECM. The modified signal returns to the ECM as the fuel temperature input. The sensor uses a thermistor which is sensitive to the change in temperature. The electrical resistance of the thermistor decreases as temperature increases.
<Reference data>

Fluid temperature [°C (°F)] | Voltage* (V) | Resistance (kΩ)
20 (68) | 3.5 | 2.3 - 2.7
50 (122) | 2.2 | 0.79 - 0.90
*: These data are reference values and are measured between ECM terminals 42 (Fuel tank temperature sensor) and 128 (sensor ground).