Fuel Rail Pressure Temperature (FRPT) Sensor

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The temperature component of the FRPT sensor is a thermistor device in which resistance changes with temperature. The electrical resistance of a thermistor decreases as the temperature increases, and resistance increases as the temperature decreases. The varying resistance affects the voltage drop across the sensor terminals and provides electrical voltage signals to the PCM corresponding to temperature.

The pressure component of the FRPT sensor provides a signal to the PCM indicating fuel rail pressure. The PCM supplies a 5 volt reference (VREF) signal, as well as supplying 5 volts on the FRP circuit. As pressure increases, the sensor signal voltage decreases.

The FRPT sensor measures the pressure and temperature of the fuel in the fuel rail and sends these signals to the PCM. The PCM uses the fuel pressure and temperature sensor inputs to command the correct fuel pump speed. The relationship between the fuel pressure and the fuel temperature is also used to determine the possible presence of fuel vapor in the fuel rail. The FRPT sensor is located at the top of the left fuel rail.

Courtesy of FORD MOTOR CO.