The Department of Justice announced it will no longer go after criminal charges for tampering with onboard diagnostic devices, but that doesn’t mean truck drivers can start installing a DEF/DPF delete kit.
For years, truck drivers have been airing grievances over diesel exhaust fluid (DEF) and diesel particulate filter (DPF) requirements. In addition to engine derate, many truckers have complained about negative impacts on engine performance and lifespan.
Some drivers have attempted to circumvent these issues with delete kits that reprogram the ECU. By tapping into the onboard diagnostics port, delete devices can stop the engine from looking for emission sensors that regulate DPF and DEF components.
There are two problems with delete kits. First, they will void a warranty. Second, they are illegal.
Per the Clean Air Act, tampering with emission controls is a federal crime. There are also civil penalties up to $45,000 per vehicle and per day for reporting and recordkeeping violations. Fines up to $4,500 per tampering event or sale of a delete device can be handed down to anyone selling or manufacturing them.
In December 2024, Wyoming diesel mechanic Troy Lake was sentenced to one year in prison for installing delete kits.
Lake’s case caught the attention of high-level officials in Washington, D.C.
Last October, Sen. Cynthia Lummis, R-Wyo., introduced the Diesel Truck Liberation Act. The bill would prevent individuals from being prosecuted or sued for tampering with emission equipment, among other things related to delete devices.
A month later, President Donald Trump pardoned the 65-year-old mechanic.
“This case is yet another example of how federal agencies have been weaponized by Democrat administrations against hardworking Americans,” Lummis said in a statement. “I’ll continue fighting to ensure this kind of government abuse never happens again. I’m thankful that Troy and his family can now put this injustice behind them and move forward – they deserve it.”
Lummis’ bill appears to be going nowhere, but anyone installing delete kits may be off the hook from criminal charges for at least the next three years.
On Jan. 21, the Department of Justice’s Environment and Natural Resources Division announced it will “no longer pursue criminal charges under the Clean Air Act based on allegations of tampering with onboard diagnostic devices in motor vehicles.”
Today, @TheJusticeDept is exercising its enforcement discretion to no longer pursue criminal charges under the Clean Air Act based on allegations of tampering with onboard diagnostic devices in motor vehicles.
— DOJ Environment and Natural Resources Division (@DOJEnvironment) January 21, 2026
That marks a major shift from the DOJ’s previous approach to delete kits. According to Environmental Protection Agency records, the agency resolved 17 Clean Air Act vehicle and engine enforcement cases in 2024, 30 in 2023, 33 in 2022 and 42 in 2021 during the Biden Administration. During Trump’s first term, the EPA resolved an average of 38 cases each year.
However, truck drivers and diesel mechanics are not completely in the clear to delete DEF/DPF controls.
The DOJ said the department and the EPA will still pursue civil enforcement “when appropriate.”
“DOJ is committed to sound enforcement principles, efficient use of government resources, and avoiding overcriminalization of federal environmental law,” the DOJ Environment and Natural Resources Division posted on social media. “In partnership with the @EPA, DOJ will still pursue civil enforcement for these violations when appropriate.”
While truck drivers can avoid criminal charges for tampering with DEF/DPF components, they can still face steep civil penalties. It is not clear under what conditions civil enforcement will be considered appropriate. The DOJ referred Land Line to the social media post when asked for clarification.
The Specialty Equipment Market Association (SEMA) applauded the announcement.
“This is a welcome end to overly harsh penalties for violations that are otherwise addressed through civil enforcement,” SEMA President Mike Spagnola said in a statement. “SEMA believes in following the law, and federal law is clear with regards to tampering of emissions systems or profiting from the sales of products that enable such behavior. SEMA remains committed to working with federal regulators at the U.S. Environmental Protection Agency to ensure our industry has a voice in the development of policies impacting compliance with federal and state laws with regards to emissions and safety, and creating a path for our industry to continue its innovation.”
Trump has been clear about his mission to roll back environmental policies he considers harmful. At his direction, Congress passed a law that got rid of three California Air Resources Board rules, including Advanced Clean Trucks and the Omnibus Low NOx regulation.
Last August, the EPA announced new guidance that will alleviate some of the headaches caused by DEF rules. The agency urged manufacturers to update DEF system software in current vehicles. New standards would prevent sudden shutdowns in trucks and other diesel-powered vehicles. LL
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