Pretty much any mod you do to the car can void the warranty that is modded. So say you get HIDS for your headlights and then your shocks blow out on ya. That would be covered cause the item that was modified didnt cause the blowing out of your shocks! But if you lower your car and then the shocks blow out... your screwed! Some dealers are hard asses about warranty work and can it difficult but then some are cool with it! It varies by dealership really and/or how well you know the service manager! Cause being friends with the service manager never hurts!