Well, many states have laws specifically for that: a car manufacturer's warranty cannot be cancelled just because the owner or someone the owner paid worked on

Well, many states have laws specifically for that: a car manufacturer's warranty cannot be cancelled just because the owner or someone the owner paid worked on the car. The manufacturer's warranty can only be voided if the manufacturer can prove that the warranty claim arose directly due to the owner (or someone they paid). So if the owner changes their own oil and the rear bumper falls off? Warranty.