Where I work, we manufacture and sell can making machinery that goes for up to $1.5 million. If a customer makes unauthorized modifications, he can void the warranty. If our field service tech determines that what he did had any relationship to the problem, then it's SOL. It's no different with a new car, a washing machine, or a stereo. You mess with something that's covered, then you have nobody to blame but yourself if it goes bad and they void the warranty. If the problem with yours is in the steering wheel, then they will probably give you no argument. If it's in the dash, then say a prayer.

By the same token, I doubt that they make up reasons not to honor the warranty. Anyone with that poor a business ethic wouldn't be in business for long.