they don't know it has a rebuilt title unless you open your yapper and tell them, take it to another dealer if you already let the cat out the bagGM warranty wont cover vehicles that have a “Rebuilt title” since it was once considered a total lost for the insurance. My Yukon had rear end damage when I bought it from the auction. Doesn’t matter what type of warranty it is , they won’t cover it.
when I take my vehicles to any dealer they dont run the registration thru dmv. they check the mileage and build date which is coded into the vin
so unless the vin was somehow flagged in the entire gm system they will have no clue what it's history is other than work that was previously done at a gm dealer