Fuel Rail Pressure (FRP) Sensor
WARNING: This page is about a different car, the 2015 Jaguar XF, 2014 Jaguar XF, and 2013 Jaguar XF. However, it is still accessible from the selected car via links, so may be relevant.
A FRP sensor is located at the rear end of the fuel rail. The sensor is screwed into a threaded port in the rail and sealed with a mating taper in the rail. The sensor is connected directly to the ECM.
The FRP sensor is a metal thin film technology type sensor. Three wires connect the sensor to the ECM. The ECM supplies a 5V reference voltage to the sensor. The pressure measurement is based on the expansion of a thin steel diaphragm which is sensed by the ECM on a return signal wire which is proportional to the fuel pressure in the fuel rail.
The signal from the FRP sensor is used by the ECM as part of its calculations for the HP pump fuel metering valve operation.