So the wife and I get in the truck this morning. I do the wait to start thing and it fires right up like usual. I go to shift into drive and notice the CEL is not going off. I wait and wait a little longer, but it is definitely on. Damn! I turn-off the truck and restart, but still on. Now I'm ticked because we are leaving early tomorrow for Grandma's house. Then I remember that I just got fuel last night. Could it be? I get out and tighten the fuel cap a few clicks. BINGO, no more CEL!

So all you 6.7L owners, just be sure to give the fuel cap a try before you take your rig in for service if your CEL comes on.