Not sure how it works in the US, but normally larger warranty claims involving engine, transmission etc has to go to HQ/factory for final decissions... Smaller claims like a faulty switch etc is handled by the dealer (AFAIK).
I think that would be the problem, it's not up to the dealer to decide if your engine/trans failure is covered under warranty. They have to relay all info to BMW HQ, or have HQ look into the electronic logs etc. I know that on my car there was a problem with the electronics that the local dealer couldn't figure out. They transferred all of the data to the factory in Germany who found out it was a loose wire...
Since warranties are covered by BMW and not the dealer, it's understandable that BMW HQ wants to make sure that if they pay for a new engine. or similar, then it's because of it being their fault. Not some aftermarket tune... They would rather check that for themselves than have a "friendly" dealer decide that BMW has to pay. After all, your service manager and dealership doesn't have to cover the warranty claim. Meaning that it might be easier for them to let BMW take the bill instead of risk loosing a customer that's not happy with their decision.
That's also how the AC Schnitzer warranty works, BMW covers any warranty claim that is not related to the tune. Any failure related to the tune is AC Schnitzer's responsibility.
Last edited by Boss330; 10-13-2013 at 12:45 PM.