Campaign Targets Emissions Tampering Practices and Proposed Policies that Facilitate Them

Washington, D.C. — The Diesel Technology Forum (DTF) is launching a nationwide education and outreach campaign to discourage diesel engine tampering and to educate legislators about state legislative policies that could encourage it.

Due to their unique combination of power, endurance, reliability, and efficiency, diesel engines are highly valued tools of work. In order to reduce emissions and achieve near zero levels today, manufacturers have spent billions of dollars in the last two decades, according to Allen Schaeffer, DTF Executive Director.

It is vital that equipment is properly fueled, maintained according to manufacturer specifications and maintained to maximize the benefits of these advanced engines. He also stated that it is crucial that we collaborate to prevent the tampering of emissions control systems and to discuss the policies that could jeopardize clean-air benefits and safety of the equipment for the operators.”

The campaign includes direct messaging to state and local policymakers and diesel users about proper care for diesel engines and equipment. As a variety of state legislatures consider so-called “right to repair/fair repair” legislation that will affect farm and other equipment, the campaign is intensifying.

These new laws generally aim to require manufacturers to give independent repair shops access to engine computer scan tool and proprietary codes. This would allow for repair of the equipment. These provisions could lead to dangerous modifications to engine emission control system components and other parts. Under the California Air Resources Board and EPA regulations, manufacturers may also be held responsible for providing a “defeat mechanism” that allows end-users bypass certain emission control inhibitors. 

In November 2020, the U.S. EPA Air Enforcement Division released a comprehensive report on the incidence of tampering in diesel engines and emission controls. It also identified software modifications to engine emission control units. Although the EPA report was focused on commercial trucks and pickup trucks, it didn’t directly quantify the extent to which tampering occurs in off-road engines or equipment. However, the agency believed this conduct occurred within almost all types of vehicles and engines. This includes passenger vehicles, commercial trucks, pickup trucks, motorcycles and forestry equipment.

The EPA has more than a dozen regulations that apply to the manufacture of diesel engines. There are also provisions in the Clean Air Act which require them to meet a variety of federal requirements regarding building and warranting their products. These requirements include testing to ensure compliance to regulations, requirements for attaining the “useful lives” provisions, which specify vehicle/engines must comply with emission standards, in-use testing requirements and making tamper resistance emissions systems. It is illegal to knowingly falsify or tamper or render inaccurate any “monitoring device and method” under the CAA (42 U.S.C. § 7413(c)(2C).

Recent news reports have highlighted pickup truck owners who “tune” their engines through software code programming and chipping. Some instances of engine programming changes that allow for pulses of overfueling have been made public and highly visible. This results in dense smoke from the exhaust, often called “rolling coal”.

“Advanced diesel emission control systems have been proven to be effective. They provide near zero emission performance for all new engines and equipment. The owners are responsible for fueling and maintaining the equipment and ensuring that they are maintained in a safe manner. To end this illegal and dangerous practice, we all must work together. It is equally important that we work together to stop this practice from being facilitated by unneeded, fair repair, or right to fix legislation. Schaeffer states that this is not good for the air quality and it can jeopardize operator safety as well as the safety of all those who use these vehicles and equipment.  


About the Diesel Technology Forum

The Diesel Technology Forum is an organization that raises awareness about the future and current role of diesel engines, equipment, as well as fuels. Forum members are experts in advanced diesel technology, emissions control, and petroleum-based as well as renewable biofuels. For more information visit

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Jessica Puchala
Diesel Technology Forum
(202) 480-6441
[email protected]
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