Welcome Paul, a few threads here with that same code:
https://www.ecodieselram.com/forum/threads/my-first-error-code-less-than-a-week-of-ownership.1612/
It seems it's one of those ghost codes that appear in really cold climates. Does that apply to you?
15K is a little to long for my liking, but if it's working for you I can't complain about that. I would be interested to see an oil analysis on your oil after 15K.
I can't say I've heard that before. Can you stop and raise the hood, and see if you can trace it down while it's running in park? Maybe have someone give it throttle in different range.
That's a fact on GM's ECM's for the Duramax. If Ram does the same, I don't know.
But yes, the dealer really has to go the extra mile to "get the goods".
I just deleted a earlier post. I refuse to let members put down others when asking a question. We're here to learn, the whole point of a forum right?
Thanks to @John @TC Diesel continuing on helping our members in this thread, that's why this forum is here. Not to say "hey, you have no idea...