The IPR solenoid receives a pulse-width modulated signal from the ECM that indicates the on and off time
the control valve is energized. The pulse is calibrated to control ICP pressure in a range from 5 MPa (725 psi) up to 28 MPa (4,075 psi). Maximum pressure relief occurs at about 32 MPa (4,600 psi).
The IPR valve is mounted in the body of the high-pressure pump. The IPR valve maintains the desired ICP by dumping excess oil back to the crankcase sump.
As demand for ICP increases, the ECM increases the pulse-width modulation to the IPR solenoid. When ICP demand decreases, the ECM decreases the duty cycle to the solenoid, allowing more oil to flow from the drain orifice.
The ECM sets Diagnostic Trouble Codes (DTCs), if the ICP electrical signal is out-of-range. DTCs are also set if an ICP signal corresponds to an out-of-range value for injection control pressure for a given operating condition.
The ECM will ignore ICP signals that are out-of-range and the IPR valve will operate from programmed default values. This is called Open Loop operation.
The ICP sensor is installed under the valve cover, forward of the No. 6 fuel injector in the high-pressure oil rail.
