I love when people just start shouting Magnuson Moss in threads like this and have no clue what the act really does. The Magnuson Moss Act does not cover you for aftermarket performance modifications or tunes it requires manufactures to honor their warranty against factory defects and not require you to use a particular brand of parts or service. Changing of the vehicle’s configuration is not covered under the warranty.
If your changes have 0 effect on the parts failed as in it literally did not or could not cause that failure then yes the MM act can protect you. At that point the failure is still a FACTORY defect. Yes if you up the redline then throw a rod or wipe a lobe that is on you. But if you say tune your trans then that AFM lifter not pumping up and wiping a lobe is not your issue as that still a defect. You are right it covers FACTORY defects unless your changes could or did cause changes in the factory parts working. The MM act has held up and helped many.
Fortunately local dealers here other than our local Ford dealer do not even try to deny warranty for programmers/tunes or even bolt on mods. They will attempt to void for a tune if they find tuned it and screwed up though as in you played with tables yourself trying to learn. Both my local GM dealer and my local Ram dealer encouraged the use of a tune to improve MPG and towing and stated it would not bother warranty unless someone obviously screwed something up. Hell my local Ram dealer didnt even care that my 2500 ran red only for the first half of its life.
Ford here on the other hand do not like to even touch a stock vehicle under warranty or recall if they can avoid it. My brother is fighting them with a focus right now.
A nice quote for you.
"In a Consumer Alert issued by the Federal Trade Commission (FTC), the agency confirmed that “The Magnuson-Moss Warranty Act makes it illegal for companies to void your warranty or deny coverage under the warranty simply because you used an aftermarket part.” The alert outlines key provisions in the law that provides protections to car owners. As defined by the FTC, an “aftermarket' part is a part made by a company other than the vehicle manufacturer or the original equipment manufacturer.”
“The FTC’s reference to aftermarket parts is equally applicable to specialty parts,” said Russ Deane, SEMA’s General Counsel. “Under the Magnuson-Moss Warranty Act, the warranty cannot be conditioned to a specific brand of parts, services or vehicle modifications unless those parts or services are provided free of charge.”
The alert notes that a consumer has the right to patronize independent retail stores and repair shops for parts and service without fear of voiding the new car warranty. The dealer/vehicle manufacturer has the right to deny a warranty repair but they must demonstrate that the aftermarket part caused the problem. The warranty remains in effect for all other covered parts."
They have the right to Deny the coverage but if fought which can be expensive then they have to prove the correlation. The act does not state you can just scream MM act at the service writer and it they suddenly jump and fix it and say okay. But it does provide a option to fight to keep coverage. Often times it will not be worth that fight. A denied warranty repair for something like HP fuel pump really wouldn't be worth it. But a denied warranty for a engine and transmission replacement after the flywheel bolts sheer and everything gets trashed (unrealistic example scenario) would be worth it.
