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EPA announces fix for truckers plagued by speed and power loss caused by diesel exhaust fluid systems
On Tuesday, the U.S. Environmental Protection Agency (EPA) announced action to address concerns from truckers and farmers about diesel exhaust fluid (DEF) systems.
On August 12, 2025, EPA Administrator Lee Zeldin announced new guidance meant to “protect American farmers, truckers, and other diesel equipment operators from sudden speed and power losses caused by diesel exhaust fluid (DEF) systems.”
EPA To Put A Stop To DEF Slowdowns
The EPA’s action will include calling on manufacturers to update DEF system software in existing vehicles and equipment to prevent sudden speed and power loss, giving truckers and other operators extra time to repair faults without impacting productivity or safety.
Currently, a DEF-fault can result in drastically reduced vehicle speeds of as little as 5 m.p.h., or the vehicle could be rendered completely inoperable, causing “significant disruptions in logistics, agriculture, and construction,” according to the EPA.
Although this derate strategy was intended to ensure compliance with EPA’s Tier 4 Emissions Standards, it has caused needless frustration, operational delays, and real economic hardship for countless farmers, truckers, and equipment operators,” officials said.
From the EPA:
“Starting with model year 2027, EPA requirements state that all new diesel on-road trucks must be engineered to avoid sudden and severe power loss after running out of DEF. To fix the problem for vehicles already in use, EPA’s new guidance, developed in collaboration with manufacturers, will work to ensure that the necessary software changes can be made on the existing fleet. In addition to providing certainty to manufacturers about how EPA wants this issue resolved, the agency is not requiring separate approvals beyond that provided in EPA’s guidance. This ensures that bureaucratic steps do not delay manufacturers’ ability to put solutions into the field.“
Current DEF System Is “Unacceptable”: EPA
“We have heard loud and clear from small businesses across the United States that the current DEF system is unacceptable. It is unacceptable that farmers, truckers, construction workers, and many other small businesses continually experience failures of diesel-powered equipment when they need it most—costing millions of dollars in lost productivity,” said EPA Administrator Zeldin. “Today, we are responding to those concerns by calling on manufacturers to take action to update their software and eliminate the unnecessary sudden loss of power and frustrating shutdowns that too many Americans have experienced.”
“The Trump Administration is fighting for farmers and truckers, as evidenced by the EPA’s new DEF guidance which is a big win for the millions of small businesses who rely on diesel engines – and who have been crushed by years of costly Green New Scam regulations,” said U.S. Small Business Administrator Administrator Kelly Loeffler. “This change will save family farms an estimated $727 million per year and offers vital financial and operational certainty. I’m proud to work alongside EPA Administrator Lee Zeldin to reduce red tape for our nation’s producers and deliver real relief for hardworking Americans.”
Trucking groups like the Owner-Operator Independent Drivers Association (OOIDA) applauded the EPA’s action.
“OOIDA and the 150,000 small-business truckers we represent thank Administrator Zeldin for listening to the men and women behind the wheel who keep America’s economy moving. EPA’s guidance establishes more commonsense inducement schedules that will help drivers maintain safe control of their vehicles as they diagnose and remedy faulty DEF/SCR systems. More flexible inducement speeds and times will help truckers finish their trips, plan for necessary maintenance, and avoid parking their truck for an extended period simply because of a false alarm. Nonsensical inducement rules have sidelined small-business truckers for too long and this accelerated relief shows what can be achieved when regulators hear directly from the people doing the job. We look forward to continued engagement with Administrator Zeldin and his staff to implement additional emissions solutions that better reflect the realities of trucking,” said OOIDA President Todd Spencer.