In all my 20 years as a dealership mechanic I have only had to have my zone tech and warranty administrator void any vehicles entire warranty a total of one time. The customer had obviously modified the vehicle so heavily and recklessly abused and damaged the vehicle that Chrysler would not warranty any portion of the vehicle. It was a 2008 RAM 2500 6.7 Cummins truck.
Of all the vehicles that have come in the doors that have been modified I have never had Chrysler or my Service Manager tell me not to warranty a repair. I have worked for quite a few dealers over the years. I have only found one vehicle that I thought a customer modification had caused a failure on a 5.9 Cummins to the point where I had to replace the long block and Chrysler still covered the repairs to a total of $18,000 in warranty parts and labor.
The one thing I have recommended to my customers over the years is honesty. I have also recommended creating some type of relationship with the shop you are dealing with. If you are a repeat customer and have built a service history with your vehicle you are more than likely not going to have any warranty issues.
When a customers vehicle comes in with a problem I as a mechanic want to know the whole story. That way you dont get a shocking quote with a ton of diagnostic labor on it because I am going to have to spend a ridiculous amount of time on your vehicle to find a problem that was created by your modification. Just tell me up front what happened so I know what I am working with.
With that being said, I have had a few vehicles of the years where a customer didnt give us the full story and I spent a bunch of time on diag. only to find a modification was installed and removed and I chased my tail trying to pin down the culprit. The way these were handled is pretty common at the dealers I have worked for over the years. We tell the customer that we found that their modification caused the issue and they were required to pay for the repair out of pocket to keep their failed parts warranty intact afterwards. If the customer agreed to pay for the repairs then Chrysler was more than happy to keep the parts and the vehicles warranty in good standing. Now, if the customer was unruly and didnt want to pay for their screw ups then Chrysler only denied any future warranty repairs on that specific failed part and not the entire vehicles warranty. As one of the earlier posters had said, the Moss-Manguson Act provides the customer certain protections under the Act.
In Chrysler's eyes, why are we paying for a part(s) and labor that failed because of something you did? We, Chrysler, pay for parts and labor when something failed on its own without outsider influence under the basic warranty. That is their philosophy.
For reading purposes, here is an excerpt from the FTC and SEMA about the Magnuson-Moss Warranty Act...
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.
What most people dont know is what is defined in the last paragraph here. Just because you have installed an aftermarket part that caused a failure doesnt mean that your whole vehicle warranty can be voided and denied. The vehicles warranty remains intact for all other parts covered under your remaining warranty.
I have always advised my performance and aftermarket customers to do a little research about the Magnuson-Moss Warranty Act to give themselves the knowledge they need to protect themselves against an ignorant dealer.
I hope this helps you. Good luck and happy modifying.