The FRP sensor is considered a passive sensor since the diaphragm inside it will change the internal resistance, according to the pressure applied to it. It has 3 lines which are one of ground, one of voltage supply and the third is signal. The ECM supplies the voltage so that the sensor works correctly, whose voltage is fixed since it must be able to feed the sensor and not fall.
The Fuel Rail Pressure Sensor is used to study the fuel pressure in the supply rail to the injectors, in this way the Engine Control Module (ECM) adjusts the pulse width of the injectors and thus that the air-fuel mixture is the most ideal.
The resistance of this sensor will increase as pressure and voltage do, that is, they do so linearly. In the same way, if pressure drops, resistance and voltage will do so in the same way.
The Fuel Rail Pressure Sensor (FRP) is connected directly to the fuel injection rail, which causes variations in temperature to affect it.
When replacing an FRP sensor you must be careful as it has flammable fuel.