From the day I test drove the truck (I have never owned a Chevy Duramax before been with Cummins for past 10 years) I heard a buzz noise coming from the dash/engine compartment. The salesman said it was normal and all of them did it. Well that was good for me as it was a new truck bla bla bla. But then with the integrity issues I have had with that dealership and salesman (some of you may have seen other threads where they lied about simple things like the truck having a diesel owners manual supplement) I decided today to look it up. I didn't find anything on it here but I did find it on a couple other forums. Turns out the sound I hear might be something a technical service bulletin has been release on, TSB # is PIP4826 Guess I'll call my dealership that I have been working with that I trust about it and see what they say. Figured I would post about it here in case others had the same thing or knew more about it. Here is the main site I found the answers (hope it is ok to link to them) I just wanted you to know my source but I also wanted to make sure this forum had the info so that no one would have to go elsewhere next time. This one even has a photo of what one guy did to fix it himself: http://www.dieselplace.com/forum/showthread.php?t=436847 - - - Updated - - - PS, the fix is to turn one of the hoses 60 degrees counter clockwise.