P1211 Code
 

New to this site, new to working on diesels. Now that the weather here in the PNW is turning agreeable, I'm tackling this nagging issue with my truck. I've done a lot of research on it, just looking for some prioritization of what/how to check first.

Issue is when I am on the throttle for more than 7 seconds, the CEL comes on with P1211. ICP looks fine, no oil. Truck has 144K. I was told by PO that the injectors were done 20K ago, but who knows. HPOP has to be original. When CEL comes on, noticeable drop in power, if I clear it, noticeable improvement. Very consistent, and it gets better the warmer the truck gets.

I used a ScanGuage II to get some ICP/IPR numbers. If I hold constant acceleration so that IPR hits 54.9 % and hold it there for 7 seconds, 3 things happen simultaneously. CEL light comes on, IPR drops to about 32% and ICP goes from about 1700 to 23-2400. Max IPR reading I ever get is 54.9 and max ICP is about 2500. Note, it is not just hard acceleration, I have a long hill and I can not make it up that hill without the CEL no matter how easy I am on the throttle.

I suspect a leak in the HP system, maybe injectors? Or weak HPOP, or IPR. What should I check first?

Thanks!