Yes you can see all codes by pulling the fuses just not in the same detail as with the code reader.. nearest dealer is a few hours away and it won't connect to generic obd2 readers.
Basically limp mode will cut power and seems to run rough...pull over turn truck off for about 5 seconds turn back on runs normal and runs great.
I originally thought fuel but I have been through the fuel system and can't find a problem..
Like I said stay around 22 psi boat and she runs great all day
I kind of assumed there would be a light as well but nothing.
I have been reading lots on the cummins forum..similar bosch injection system and seems to be cummins guys going into over boost and then limp mode with no codes either.
I am open to ideas but I have a spare turbo think first step I will try that wastegate and see what happens.