http://www.sema.org/warranty/

http://www.sema.org/warranty/atta.cfm

"Clean Air Act Warranty Provisions (42 U.S.C. S 7541 (C) (3) (B))

The federal Clean Air Act requires vehicle makers to provide two emissions-related warranties -- a production warranty and a performance warranty. The production warranty requires the vehicle maker to warrant that the vehicle is designed, built and equipped so that it conforms with emissions requirements at the time of sale. The performance warranty requires the vehicle maker to warrant that the vehicle will comply with applicable emissions requirements as tested under state vehicle emissions inspection programs for the warranty periods specified in the law (for model year 1995 and later vehicles, the warranty is 2 years/24,000 miles for all emissions-related parts and 8 years/80,000 miles for the catalytic converter, electronic emissions control unit and on-board diagnostic device). The performance warranty is conditioned on the vehicle being properly maintained and operated.

Like the Magnuson-Moss Act, vehicle manufacturers may not refuse warranty repairs under the Clean Air Acts performance and defect warranties merely because aftermarket parts have been installed on the vehicle. The only circumstance under which the vehicle manufacturer can void the emissions warranties is if an aftermarket part is responsible for (causes) the warranty claim."

The following is from Ford's 2001 warranty booklet:

EMISSIONS DEFECT WARRANTY COVERAGE
Under the Emissions Defect Warranty, Ford Motor Company provides coverage for 3 years or 36,000 miles (whichever occurs first). This is an
extension of the federal requirement that calls for coverage of 2 years/24,000 miles (whichever occurs first) for passenger car and light
duty trucks. Certified heavy duty engines (vehicles with a GVWR over 8,500 pounds) are provided coverage for 5 years or 50,000 miles
(whichever occurs first).
During this coverage period, Ford Motor Company warrants that:
² your vehicle or engine is designed, built, and equipped to meet - at the time it is sold - the emissions regulations of the U.S. EPA.
² your vehicle or engine is free from defects in factory-supplied materials or workmanship that could prevent it from conforming with
applicable EPA regulations.
² you will not be charged for repair, replacement, or adjustment of defective emissions-related parts listed under What is Covered? on
pages 13-14.

Under the Emissions Defect Warranty for passenger cars and light duty trucks (vehicles with a GVWR of 8,500 pounds or less), Ford Motor
Company also provides coverage, including labor and diagnosis, for 8 years or 80,000 miles (whichever occurs first) for these emissions parts:
² catalytic converter
² compuvalve
² electronic emissions control unit (PCM)
² onboard emissions diagnostic device
² vehicle communication link (VCL) module

EMISSIONS PERFORMANCE WARRANTY COVERAGE
If your vehicle is registered in a state where the state or local government has an EPA-approved inspection and maintenance program, you may also be eligible for Emissions Performance Warranty Coverage for 2 years or 24,000 miles (whichever occurs first), if you meet certain conditions.
Under the Emissions Performance Warranty for passenger cars and light duty trucks, Ford Motor Company also provides coverage, including labor
and diagnosis, for 8 years or 80,000 miles (whichever occurs first) for these emissions parts:
² catalytic converter
² compuvalve
² electronic emissions control unit (PCM)
² onboard emissions diagnostic device
² vehicle communication link (VCL) module

I hope this helps you in your repairs.