Injection Pressure Regulator (IPR)
The IPR is a PWM variable position valve that regulates the pressure in the ICP system. The IPR restricts the return flow path for oil from the high pressure pump. As the duty cycle increases, the IPR restriction to the drain increases, thus increasing the ICP. The IPR duty cycle is controlled by the PCM and is modulated from 0 to 65% depending upon the desired injection control pressure.
When the starter is engaged and the engine fails to start, the IPR command increases toward its maximum until the engine starts. The normal range for the IPR at idle is between 16-24%. An above 24% range indicates high effort or higher commanded ICP to achieve idle. A below 16% indicates low effort to achieve idle.
An open circuit results in minimal oil pressure and a no-start situation. A short to ground in a circuit results in maximum oil pressure, limited by a mechanical pop-off valve to 27,580 kPa (4,000 psi).