The IPR valve works hand in hand with the ICP sensor.... any change to IPR duty cycle is going to change injection control pressure.

Here's how it works.... the ICP sensor reports injection control pressure to the PCM. The PCM knows what it needs for ICP and adjusts the duty cycle of the IPR to achieve it (some scan tools can display ICP as well as ICP_DES) and then rechecks the ICP reading to see if it has what it wants.

We cannot physically change IPR% (the % being the duty cycle or <ON> time versus the <OFF> time of the current in the circuit). The PCM is constantly adjusting IPR to maintain what ICP is required for a given operating circumstance.

Now.... if we see IPR duty cycle higher than expected, we can assume (but this is not necessarily a safe assumption) that there MAY be a concern with our oil quality/condition/level... or there MAY be a high pressure oil system leak.... There MAY be a spilling injector... an HPOP internal concern... an IPR valve concern or even a combination of circumstances or events. There are too many variables to even begin any diagnosis based on an IPR reading that we "think" is high without some reason to do so.....


IPR percent is a PCM output - Increase IPR and we increase ICP (this is, basically, a "feedback" type system).