Originally Posted by Doru

Could be the oil in the transfer case in need of change. That oil is quite expensive, but you don't need much of it. The problem is, you need to re-initialize the transfer case after changing it - only with GT1 you can do it. And the transfer case will throw that code if I'm not mistaken, once the oil has a certain mileage on it. Only for the 2004+ e53. I changed that oil this past spring, and it's very easy, but you need the scanner.