They way it should be or is in most cases is, they have to prove the aftermarket part caused the issue. Use to have a Cobalt with mods on it. Went in for warranty work because my reverse lights weren't coming on. Tech said "the switch box under the shifter broke but you have a cold air intake so warranty is voided" I stated they had to prove the part caused the issue and he said that is correct. Once that got brought up they warrantied it.