DTC P0091: Fuel Pressure Regulator 1 Control Circuit Low: General Description

The PCM operates the fuel pressure control valve with the signal from the fuel rail pressure sensor to control optimized RPM and rail pressure.

The high pressure pump adds high pressure to low pressure fuel from the low pressure pump. The fuel pressure regulator controls fuel pressure from 40(4 MPa/580.15 psi) to 150 bar (15 MPa/2175.57 psi). Under the abnormal condition of high pressure fuel system, the PCM controls fuel system as low pressure.