An official website of the United States government.

This is not the current EPA website. To navigate to the current EPA website, please go to This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »


Performance Diesel, Inc. Clean Air Act Settlement Information Sheet

(Washington, DC - September 12, 2019) Today, the U.S. Department of Justice and the Environmental Protection Agency (EPA) announced a settlement with Performance Diesel Inc. (PDI) to resolve alleged violations of the Clean Air Act (CAA) associated with the manufacture, sale and installation of aftermarket products that defeat the emissions control systems of heavy-duty diesel engines.  As part of the settlement, PDI has agreed to stop the sale of all products the government alleges violate the CAA.  PDI will also pay a civil penalty of $1,100,000 over two years due to their limited financial ability to pay a higher penalty.

On this page:

Overview of Company 

Performance Diesel, Inc. (“PDI”), is a Utah corporation owned and managed by its president Jerad Wittwer. PDI’s principal place of business is in St. George, Utah. PDI also uses a warehouse in Zelienople, Pennsylvania. PDI conducts its business both from its Utah store and over the internet through its website,, selling to individual customers directly as well as to downstream retailers.

Top of Page


PDI manufactured, sold, or installed at least 5,549 aftermarket defeat devices. These products were for heavy-duty diesel engines (“HDDEs”) which power some of the largest trucks on public roads. The aftermarket products sold by PDI include hardware components and electronic tuning software, known as “tunes,” that hack into and reprogram a motor vehicle’s electronic control module to  alter engine performance and enable the removal of filters, catalysts and other critical emissions controls that reduce air pollution. PDI’s aftermarket products are designed for use with numerous models of HDDEs manufactured by Caterpillar, Cummins, Detroit Diesel, International, and Paccar for model years 1993-2020.

PDI manufactured, sold, and installed parts or components for motor vehicles and motor vehicle engines that bypass, defeat, or render inoperative elements of design that were installed by the vehicle or engine original equipment manufacturer to comply with CAA emission standards. Accordingly, EPA alleges that each sale constitutes a violation of section 203(a)(3)(B) of the Act, 42 U.S.C. § 7524(a)(3)(B), and each installation by PDI which renders inoperative a motor vehicle or motor vehicle engine’s device or element of design constitutes a violation of section 203(a)(3)(A) of the Act, 42 U.S.C. § 7524(a)(3)(A).

Top of Page

Injunctive Relief

The Consent Decree specifies steps PDI must take to prevent future violations. PDI may sell its products if it complies with the requirements contained in the Consent Decree. The Consent Decree contains the following injunctive relief:

  • PDI will not manufacture, sell, offer to sell, or install on any motor vehicle or motor vehicle engine any part of component, including but not limited to, tunes, software, or programming (and devices on which such tunes, software or other programming are loaded), a principal effect of which is to bypass, defeat, or render inoperative a motor vehicle emission control device of emission-related element of design absent a reasonable basis that such products do not adversely affect vehicle emissions and retain full operation and functionality of the On-Board Diagnostics System.
  • For new tuning products, PDI will demonstrate a reasonable basis by obtaining a California Air Resources Board (CARB) Executive Order (EO) prior to manufacture, sale, offering for sale, and installation of products.
  • For existing products not currently covered by a CARB EO, PDI will demonstrate a reasonable basis by submitting a complete application to CARB that covers the tunes prior to manufacture, sale, offering for sale, and installation. Under this consent decree, a complete application includes emission test results sufficient to satisfy CARB’s requirements for obtaining a CARB EO.
  • PDI must also
    • destroy or delete all products subject to the consent decree under its control, including products forfeited by employees and officers of PDI;
    • refuse, and direct its authorized dealers to refuse, to provide technical support or other information, including marketing materials, pertaining to installation, manufacture, sale, use, or repair of any product subject to the consent decree on a motor vehicle or motor vehicle engine;
    • review and revise marketing materials;
    • send notice to all customers and authorized dealers of products subject to the consent decree informing them of the settlement;
    • provide notice to employees of applicable CAA prohibitions;
    • require employees to forfeit products subject to the consent decree;
    • conduct training for all PDI employees to ensure compliance with the Act; and
    • submit semi-annual status reports on compliance with the CD.

Top of Page

Pollutant Impacts

Today’s vehicles emit far less pollution than vehicles of the past. This is made possible by careful engine calibrations, and the use of filters and catalysts in the exhaust system. Aftermarket defeat devices undo this progress, and pollute the air we breathe. The emissions impact depends on the original vehicle design, and the extent of the vehicle modifications. EPA testing has shown that a truck’s emissions increase drastically (tens or hundreds of times, depending on the pollutant) when its emissions controls are removed. Even when the filters and catalysts remain on the truck, EPA testing has shown that simply using a tuner to recalibrate the engine (for the purpose of improving fuel economy) can triple emissions of NOx.

Here, PDI’s defeat devices increased air pollution formed in the engine during combustion. They also enabled the removal of the filters, catalysts, and other emissions control systems that are necessary to treat air pollution formed in the engine before it is emitted into the ambient air.

Top of Page

Health Effects and Environmental Benefits

The Clean Air Act aims to reduce emissions from mobile sources of air pollution, including NOx. Mobile sources of air pollution contribute approximately 58% of the nation’s oxides of nitrogen emissions. EPA testing demonstrates that installing aftermarket parts can result in increased NOx emissions from mobile sources.

NOx emissions pose significant health and environmental concerns. Oxides of nitrogen form when fuel burns at high temperatures. Oxides of nitrogen can travel long distances, causing a variety of health and environmental problems in locations far from their emissions source, including ozone and smog. Oxides of nitrogen also contribute to the formation of particulate matter (PM) through chemical reactions in the atmosphere, and particulate matter can cause asthma, difficult or painful breathing, and chronic bronchitis, especially in children and the elderly.

The key health effects categories associated with ambient particulate matter include premature mortality, aggravation of respiratory and cardiovascular disease, aggravated asthma and acute respiratory symptoms including aggravated coughing and difficult or painful breathing, chronic bronchitis and decreased lung function that can be experienced as shortness of breath. Symptoms of immunological effects such as wheezing and increased allergenicity have also been observed. Diesel exhaust particulate matter is of special concern. The EPA’s Clean Air Scientific Advisory Committee has concluded that diesel exhaust is likely to be carcinogenic to humans. In addition to these health effects, particulate matter generally causes damage to, and soiling of, commonly used building materials and culturally important items such as statues and works of art. It is also a major cause of substantial visibility impairment in many parts of the United States.

Top of Page

Civil Penalty

PDI will pay a civil penalty of $1,100,000, as the company has a limited financial ability to pay a higher penalty.

Top of Page

Comment Period

The proposed settlement, lodged in the U.S. District Court for the state of Utah, is subject to a 30-day public comment period and final court approval. Information on submitting comments is available at the Department of Justice website.

Top of Page

For more information, contact:

Brianna Iddings 
U.S. Environmental Protection Agency (2242A)
1200 Pennsylvania Ave., N.W.
Washington, DC 20460
(202) 564-7581

Ethan Chatfield
Region 5
77 W. Jackson Blvd.
Chicago, IL 60604

Top of Page