That'll all come down to the balls the dealership is willing to risk, during a warranty situation.
In accordance with the Magnuson-Moss Warranty Act, in the section that protects aftermarket parts manufacturers, the vehicle manufacturer/dealer must prove in writing that the aftermarket part in question was a direct cause of the failure/reason that the vehicle is in for warranty work. Direct cause.
Lemme tell you how this worked for me... 1993 Jeep Wrangler, 3" Superlift suspension system, 33" BFG Mud Terrains, assorted aftermarket bumpers and rock rails. And Currie steering box brace.
Damn intermittent wiper control module goes out. After the first two months. Take it to the dealership, tell 'em to get that thing fixed. Asshead at the counter tells me my factory warranty is void, because "the vehicle is modified." I looked at him, said "okay," and left. Went home, dug out a copy of the Magnuson-Moss Warranty Act, and went back to the dealership. Asked that same Asshead to fix my intermittent wiper control module, UNDER FACTORY WARRANTY, and he tells me again that my warranty is void.
I asked for the dude's service manager. Now, he gets the service manager, and the guy comes out ready to run his mouth - I didn't even give him the chance... I whipped out the copy that I had, flipped to the appropriate page, and read that schit to him. His mouth was hanging open, when I asked him "How does a suspension lift, tires, bumpers and rock rails cause a wiper control module to go out? If you can tell me, right now, then you can put that same thing in writing. Right now."
He thought about it for a second, then says "Sir, can I have the keys?"
Yep - get movin', asshead...
Not many service managers will put their balls on the line to put that schit in writing. They might try, but trying isn't good enough. They have to PROVE... <thumbsup>