Obviously, as you already know, you will need to get those codes checked at autozone or similar place, any update yet on that? What year of X3 do you have and how many miles? Often, the codes are from emissions issues. The X3's are notorious for having intake/vacum leaks, due to sub-standard plastic/rubber being used on the intake boot and other hoses. After about 40K on most X3's the intake boot and such starts to deteriorate and will get cracks around the bends. When the temps start changing, this stresses the plastic even more. This is more often the problem, than not, with the engine light, but obviously could be other things as well. The hoses and boot are not covered under the maintenance, federal emissions, or extended warranties, as they are considered wear and tear items. If you throw codes like P0171 or P0174 (too lean, etc) it is an intake leak problem, hopefully not an emissions valve. Replacement boots/hoses are relativlely inexpensive, but there is a lot of stuff to remove to get to where you need to get to replace the boot and hoses, so the dealership charges a huge price tag for labor. There are lots of great deatailed DIY's out there though on forums, not massivly difficult to do, just lots and lots of stuff to move out of the way. I replaced the boot myself a little bit ago in a "Hurricane", hah, and it took me and my buddy about 4 hours to complete and instead of costing $800, it cost me $100 for the diagnostic $57 in parts and a 12 pack of beer. I recommend paying for the diagnostic from bmw or trusted local bmw mechanic, then deciding if you want to do the work yourself.