New 335d owner with a p0402 and its under warranty!!!

Hey guys. I'm a new owner of a 2010 335d with 50,000 miles with a year left on the bmw extended warranty/maintenance program. On my way to work today, my ses light popped on. I have a repair/dyno shop so I grabbed the scanner when I got to work and read the code. EGR valve insufficient flow detected. I plan on taking it into the dealer for repair since it's still under warranty. What can I expect them to do to repair this? Also, what should I ask/push them to do to repair this. I'm concerned that it could be a carbon buildup problem from what I have read. After owning 3 tdi jettas, I decided to give this car a try and absolutely love it. My only concern is the carbon buildup problem. Any help, tips, and suggestions on what I should push for the dealer to do while they have it? Thanks

New 335d owner with a p0402 and its under warranty!!!