Had the same problem, yet each time I took to the dealer they could not find a problem. I found a posting on this forum, printed it out and took to the dealer. They used it and fixed the problem.
Here in CA, it is not as cold.
Problem was only in the AM (initial start). Also it would continue thru the day if the truck was parked for a while.
Your assumptions are correct. O-rings and FICM is what needs to be fixed. At least point the Tech in that direction and he should do that at minimum. I wish I could find that posting as there may be more to it. If I do, I will get it to you. Solved my problem perfectly.
Surprised I am the only respondent to your posting. This is a common problem.
FYI ~ covered under your 5/100 engine warranty. Out of pocket $100.
Best to get it fixed before it gets much colder as it will get much worse.
