Modifying your new car won't automatically void your manufacturer's warranty. But it may cost you depending on the mod. Here is what you need to know.

I got a few questions the other day about vehicle modifications and whether a manufacturer can void your warranty over them after I mentioned the Magnuson Moss Warranty Act . A few astute readers pointed out that one of the other things Mag Moss did was forbid manufacturers from requiring consumers to use any particular brand of "article or service" to invoke warranty coverage.

The law says: "No warrantor of a consumer product may condition his written or implied warranty of such product on the consumer's using, in connection with such product, any article or service (other than article or service provided without charge under the terms of the warranty) which is identified by brand, trade, or corporate name . . ."

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So, they can't dictate what brand of parts you put on your car during the warranty period. Mr. Goodwrench, Motorcraft and Mopar are optional. But simply swapping parts is not the area of greatest concern here. The real concern is vehicle modification.

Many modifications people do to their cars fall outside of the "article or service" contemplated by the statute. Suppose you loved the way Vin Diesel could pull wheelies in 13th gear in his Charger and figured a little of that "NOS" would do the same for your car. Even if your little four-banger won't pull wheelies in any gear, it now puts out a few more horses than before. So, if you find the transmission spitting out teeth like it's been punched in the mouth by Mike Tyson, you can bet the manufacturer might blame the problem on the increased power being fed to the trans.

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The Magnuson Moss Warranty Act requires manufacturers to honor their warranties and auto manufacturers only warrant their vehicles against manufacturing defects. Your claim here could be denied because the failure was not due to a defect in a factory component. It was caused by something added to the car: the nitrous oxide injection system which was not part of your car to begin with. That system caused a non-defective part to fail. Your mod did not void the warranty. It's just that the failure was not caused by a factory defect.

Other popular modifications might likewise be problematic. Companies sell aftermarket modifications for Electronic Control Units which range from new programming to high performance replacement units. The net result is that the engine is now being controlled by a program unlike the one your car shipped with. Manufacturers know these mods exist and these will also run afoul of warranty coverage. Many Owner's Manuals specifically state that warranty coverage does not extend to changes to the vehicle's "configuration" and this limitation is not forbidden by the Magnuson Moss section cited above. The manufacturer is not requiring you to use a particular brand of item or service, they just don't want you using one that is altered to different settings than those configured at the factory. Or, put it this way: If your ECU went bad and needed replacement, you could replace it with one of any brand you liked, so long as it controlled the engine the same as the original.

Expect your warranty claim on your drivetrain to be scrutinized if you come in with a hopped up ECU. These claims are routinely denied so long as the failure appears to be related somehow to the new - altered - performance parameters of the ECU. And this is perfectly legal according to the Federal Trade Commission which is the government entity charged with creating rules to implement the Magnuson Moss Warranty Act.

Many factory warranties also broadly exclude coverage for "racing" or "high performance" aftermarket parts and failures associated with them. Again, manufacturers can legally do this. If you slap a high performance cam in the engine and the engine fails, the manufacturer will likely argue that the cam caused something else to fail which would not have failed but for the bumpy cam you threw it. Is this fair? Depends on how you look at it. Read any Owner's Manual you can get your hands on and you will see these warnings. Some might argue that you shouldn't have bought the car if you disagreed with these limitations.

Obviously, an aftermarket camshaft or a hopped up ECU won't void the entire warranty on your car. The master cylinder failed? The blue tooth quit working? Unless there is a logical connection between the mod and the part or system that failed, you should be good to go.

Keep in mind that some modifications can be undone if need be. I had a client whose stalling complaints were dismissed because he had a K&N air filter on his vehicle. If he had simply swapped the factory air filter back in before he had gone in for warranty work, the claim would probably have breezed through like any other. Instead, when the dealer could not find the problem with his engine someone pointed at the air filter and said, "That's it." (We rectified that decision later with some litigation.)

I know there are many mods - like the one pictured above - you can't just swap in and out whenever you feel like it. In those instances, be prepared to intelligently make the case for why that mod did not cause the problem you are complaining of. And if the dealer shoots you down, ask to speak to someone from the factory if they haven't already been consulted.

I've had people tell me that the seller of the performance parts assured them that the new parts would not affect their warranty coverage. To that, all I can tell you is that they are not the one who has the final say on that; it's the manufacturer. Perhaps you should show them where your Owner's Manual addresses aftermarket racing parts and configuration changes to the vehicle. Ask how their product does not fit in those categories.

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Also, there is a lot of confusion about the FTC's "Consumer Alert" on aftermarket parts which is referenced above. To be clear, the FTC explicitly said: "the manufacturer or dealer must show that the aftermarket or recycled part caused the need for repairs before denying warranty coverage." Once they have done that, they are all set. And the FTC's ruling did not sanction alterations, modifications or racing and high performance parts. The ruling addressed "Auto Warranties & Routine Maintenance." That is why it was called, "Auto Warranties & Routine Maintenance." It was not called "Warranty Coverage Guaranteed for Your Chipped Nitrous-Breathing Ride."

So, you can use any type of part or service you want during the warranty period so long as it does not alter or reconfigure the car from its factory specs. In the cases which do, you might run into problems getting warranty coverage for failures associated with those parts or modifications, especially if the parts are designed for racing or high performance. And as always, consult with a local attorney when in doubt.

Follow me on Twitter: @stevelehto

Steve Lehto is a writer and attorney and has been practicing consumer protection and lemon law for 23 years in Michigan. He taught Consumer Protection at the University of Detroit Mercy School of Law for ten years and wrote The Lemon Law Bible. He also wrote Chrysler's Turbine Car: The Rise and Fall of Detroit's Coolest Creation and The Great American Jet Pack: The Quest for the Ultimate Individual Lift Device.