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

The ECM/PCM monitors the signal (voltage) from the Fuel Rail Pressure Sensor (FRPS); the ECM/PCM then commands the Fuel Pressure Control Valve (FPCV) to increase or decrease fuel pressure.

The low fuel pressure pump supplies fuel to the high fuel pressure pump driven by a camshaft lobe. The FPR controls high fuel pressure from 40bar (4MPa/580.15psi) to 150bar (15MPa/2175.57psi). Under abnormal high pressure fuel system conditions, the ECM/PCM goes into limp-home mode and high fuel pressure is maintained the same as low pressure system.