Fuel Rail Pressure (FRP) Sensor

WARNING: This page does not describe the selected car, but rather 31 other vehicles, including the 2006 Mercury Mountaineer, 2006 Mercury Monterey, 2006 Mercury Montego, 2006 Mercury Milan, and 2006 Mercury Mariner. However, it is still accessible from the selected car via links, so may be relevant.

The FRP sensor is a diaphragm strain gauge device in which resistance changes with pressure. The electrical resistance of a strain gauge increases as pressure increases, and the resistance decreases as the pressure decreases. The varying resistance affects the voltage drop across the sensor terminals and provides electrical signals to the PCM corresponding to pressure.

Strain gauge type sensors are considered passive sensors. A passive sensor is connected to a voltage divider network so that varying the resistance of the passive sensor causes a variation in total current flow. Voltage that is dropped across a fixed resistor in series with the sensor resistor determines the voltage signal at the PCM. This voltage signal is equal to the reference voltage minus the voltage drop across the fixed resistor.

The FRP sensor measures the pressure of the fuel near the fuel injectors. This signal is used by the PCM to adjust the fuel injector pulse width and meter fuel to each engine combustion cylinder.

Fig 1: Identifying Fuel Rail Pressure (FRP) Sensor

Courtesy of FORD MOTOR CO.