That would be my opinion ( I say opinion as I have not verified) but how or why would a simple headlight circuit (for example) go through a PCM, (or GEM or whathaveyou). I know simple things can still be tied to a signal conditional thing such as a chime (headlights on KOEO), or dome lights due to door open, etc. A PCM seems overkill to be always hot.

Wiring diagrams for basic circuits start as upstream as a region that states "Always hot", I would assume a PCM shuts down and wouldn't apply to simple circuits..

Maybe Im getting off topic, but its hard to know who to believe these days, and of course nobody around my area actually knows Diesels so I have yet to find an amazing mechanic (didn't say tech! ha)
I could have said 'knows electrical', but when in doubt people blame Diesel issues they don't understand, IDM, and other modules only muddy the waters.

 

Well its been a while, -my apologies...

The 'official' issue per the shop, was loose battery terminals. I had never tried aggressively loosening them as much as the mechanic did, and supposedly this was required...

Apparently, "very tight and perfect" should be the way to best describe battery terminals. Anything less than that isn't good enough.

No issues so far! Its been at least a week or 10 days i think, so thats promising!

Last point: Truck cranks SO MUCH FASTER its insane... Feels like a different truck while starting! Its so nice! And less smoke at startup, due to better ignition!! Very thrilled about this!