High-flow catalytic converters (HFCs) are aftermarket emission control devices designed to improve a vehicle's power and fuel economy. While they are legal in many states, HFCs are not street legal in California. Installation of an HFC on a vehicle can void its emissions warranty.
Federal law requires that all new vehicles sold in the United States must be warranted against defects in materials and workmanship for at least three years or 36,000 miles, whichever comes first. The Magnuson-Moss Warranty Act, 15 U.S.C. 2302(c), requires automakers to provide consumers with clear and concise information about their warranties in owner’s manuals and other written materials provided at the time of sale.
An automaker may void all or part of a vehicle’s emissions warranty if the owner modifies the vehicle so that it no longer meets federal emissions standards required when the vehicle was sold. This includes installing parts that have not been certified by the Environmental Protection Agency (EPA) as replacements for original equipment manufacturer’s parts. Automakers also may void warranties if owners don’t follow proper maintenance schedules or use only fuel, oil and other fluids that meet the automaker’s specifications.
The EPA has established guidelines that automakers must follow when voided warranties due to modifications made by vehicle owners. These guidelines state that an automaker cannot deny a warranty claim simply because a car has been modified; there must be a causal link between the modification and the need for repairs before denial is permissible. Additionally, an automaker cannot deny coverage under circumstances where repairs would not have been necessary if not for the presence of the modification – even if such repairs are related to normal wear and tear items like brakes or tires.