"The vehicle manufacturer is not allowed to void the vehicle warranty just because aftermarket equipment is installed on the vehicle. This protection for consumers is the result of a parts self-certification program developed by the Environmental Protection Agency (EPA) and the Specialty Equipment Market Association (SEMA).
"Under the program, if a parts maker completes the EPA process of self-certifying its parts, the vehicle manufacturer cannot void the warranty even if the certified part has failed and is directly responsible for the warranty claim. In cases where such a failed aftermarket part is responsible for a warranty claim, the manufacturer must arrange a settlement with the part manufacturer, but the new vehicle warrant is not void under the law.
"If the failure to honor a claim involves the new-vehicle warranty, and it appears that the manufacturer is improperly denying a claim, the incident should be reported to the Federal Trade Commission (FTC). The FTC is responsible for monitoring compliance with the warranty law; the agency's telephone number is (202)326-3128."