So your talking about the 4.8 X, not the 4.6, right? If the 4.8, this has happened to my cousins 4.8, he took it in, dealer said it is a computer thing. Sometimes when you shut off the car after pulling in to the drive way or street, and then quickly shut off, what happens "per SA" is the computer didn't have time to adjust. All you have to do is start it up, wait like 30 sec. and then turn it off. Everything should be fine. I still think that this sounds ridiculous. But if I argue, who will listen . Good Luck.