The Fuel Pressure Regulator Valve (FPRV) controls pressure of the common rail regulating fuel flow on normal driving. The ECM senses a rail pressure sensor signal, RPM and accel pedal sensor signal and controls proper rail pressure using duty for current driving condition. Current of the fuel pressure regulator valve is decreased then more fuel flow to the commom rail and rail pressure is increased.

Current of the fuel pressure regulator valve is increased then less fuel flow to the commom rail and rail pressure is decreased.If the fuel pressure control valve circuit is open or connector is disconnected, current of the fuel pressure regulator valve set "0". Then, the fuel flow rate of the common rail increase to the maximum.