The rail pressure-control valve sets the correct pressure in the rail as a function of engine loading, and maintains it at this level. If the rail pressure is excessive, the pressure-control valve opens and a portion of the fuel returns from the rail to the fuel tank via a collector line. If the rail pressure is too low, the pressure-control valve closes and seals off the high-pressure stage from the low-pressure stage. Rail pressure control valve is intgrated in high-pressure pump.

At after run test mode or fuel cut mode, if within set time engine rpm is not dropped below the lower set value, error is detected. The reasons are short circuit, connecting resistance, faulty rail pressure sensor, continuity of fuel pump relay, faulty rail pressure control valve, defective high pressure pump, ECU fault, etc.

Refer to P1182, P1183 DTC inspection procedures.