hello,
I had the exact same issue, and I had the check engine light come on and go off by itself. Went in to talk to the service rep, and here is what fixed the problem.

Unplug everything that is connected to the idrive- phone, iPod any cigarette lighter connected devices. Pop the navi DVD out. Drive the car for a good bit and let it sit (Park, lock it down). Change the battery on your key fob as well (if you have Comfort Access). iDrive will respond by resetting its basic settings and things should go back to normal.

Good luck.

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2007 4.8i Space Grey, 20", black nevada interior
All options with no 3rd row, rear entertainment,
handling pkg.