[cfjara]

I'm sure dealer wouldn't notice the ECM swap unless they were looking for it. Ultimately every part that goes into the car is scanned into a database on the manufacturing line. But i'm sure this is something the dealer is far removed from. I would think if Saturn corp was in litigation over a warranty issue, they could figure out by the serial number on the ECM that it was not the one the car was built with.

When you swap you ECM, the programmer needs to flash the new ECM with your VIN number. This keeps everything happy.