Breaking News....in my desperate search for answers I found someone experiencing my exact situation on the website Diagnostic Network. I was able to reach out to this person and they just gave me the low down on what happened. Here's his story.......copied and pasted from my email
Yeah no problem at all I remember the hell I went through to try to figure this one out so I'm glad I can potentially help. So it sounds just like what I went through, the truck would start on the stock tune file via jumping starter relay, of course all kinds of codes.
Previously to me working on the truck the customer had got the oil pressure sensor replaced and supposedly the truck ran and drove for a little bit maybe a day and right back into the same scenario. I got the truck, I scoped all kinds of signals. Couldn't really come up with anything other than the fuel injector pulse width was shorter. When I say shorter I mean only having two pulses when it died instead of three on a normal running engine. it threw me for a loop because it appeared like the PCM was simply kinda slowly starving the engine of fuel. (I compared the pulse with to other ecodiesels.) After finding the pulse on the ejector being the only thing that appeared different I assumed the PCM was faulty. At this point I didn't realize the truck runs on the stock file. So I replaced the PCM and it ran great until I put the tune on it. Thinking there was something with the PCM going into limp mode with all the codes on the stock file I dug some more. Miraculously a guy and I believe he was from Ohio reached out to me via Diagnostic Network post and said he had a similar experience and a different tune solved the problem. So I took the leap bought another tune and voila problem gone.
I went through Sierra Industries, Alberta . Using HP Tuner.
Also worth noting is the fact that this truck also ran for half it's life on this tune. And i reached out to the original tuning company EOC. And they said it couldn't be the tune because it ran for so long with no problem. However after I figured out the problem I was pretty frustrated so I wanted to make sure they realized that their tune can make this fault in case someone else asks them. Eventually I received an answer that stated as much, yes they realized that there is a problem like this. 🤔