The FRP is a 3-wire variable capacitance sensor. The FRP produces a linear analog voltage that indicates pressure of the high pressure fuel system.
The PCM monitors fuel rail pressure as the engine is operating to control fuel pressure. This is a closed loop function which means the PCM continuously monitors and adjusts for ideal fuel rail pressure determined by conditions such as load, speed and temperature.
IDS: FRP (volts) and FRP_A (pressure)