I got the X5 back today. It turns out it was the NOX sensor. Apparently, the computer gave the dealer some weird codes they didn't understand which is why they had to call in a local BMWNA rep. I guess BMWNA rep has tools with additional codes. Anyways, everything looks fine, hopefully there won't be any more problems.

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2010 X5d, Space Gray, Tobacco, Premium, Tech, and rear climate packages, roof rails, spare tire, and iPod adapter.
2006 330i, Sport, 6MT