EPA issues proposal to entirely eliminate DEF ‘limp mode’ in response to outcry from truckers

The U.S. Environmental Protection Agency (EPA) announced a proposal that would eliminate Diesel Exhaust Fluid (DEF) system-related speed reductions and power losses, often called “limp mode,” in newer commercial vehicles.

EPA Seeks To Eliminate DEF Deratements In New Trucks

On July 9, 2026, EPA Administrator Lee Zeldin debuted a rule proposal to “eliminate DEF deratements entirely” for newly-manufactured vehicles and engines.

The EPA said the proposal was issued in response to “calls from American truckers and diesel operators to eliminate deratements entirely, a burdensome problem often caused by DEF system failures.”

The proposal builds on recent action taken by the EPA calling on manufacturers to update DEF system software to lessen the impact of DEF deratements for farmers, truckers, and other diesel equipment operators.

“Today, the agency is taking a historic step to provide a commonsense solution to deratements for American operators. EPA is proposing to completely remove deratements and vehicle speed restrictions for newly manufactured highway engines and vehicles and new nonroad engines and equipment, including those used in agriculture. Instead of trucks and tractors lurching to a halt when DEF systems fail, under EPA’s proposal, operators would receive visible and/or audible alerts that allow them to continue operating until they can safely address the problem,” the agency said.

The EPA is also accepting public comment on a related proposal to allow manufacturers to also implement this change for in-use on road and nonroad engines and equipment. 

EPA Suggests Additional Relief For Emissions Rules

The EPA additionally announced plans to scale back emissions warranty requirements that would “maintain the underlying emission standards, including nearly 90% of the nitrogen oxide (NOx) reductions, while sparing Americans from unnecessary warranty costs.”

The agency is also suggesting a plan to provide truck and engine manufacturers, suppliers, trucking fleets, and dealerships with additional lead time to comply with NOx emission reduction provisions of the Biden-era 2023 rule applying to Model Year (MY) 2027 and later heavy-duty highway engines. The EPA proposal would create nonconformance penalties for certain heavy-duty diesel engines that temporarily cannot meet the new NOx standards but would still allow truck sales to continue.

The EPA suggests that the proposal could “save American truckers $12 billion through commonsense revisions to unnecessary and unworkable Biden-era compliance requirements.” Savings are estimated at around $6,000 per new truck.

See this EPA Fact Sheet for additional information on the agency’s proposals.

What Are They Saying?

“Americans depend on reliable trucks to move essential goods across the country. If finalized, these changes will help manufacturers keep improving their vehicles without being forced to rush products to market before they’re ready. Combined with the Trump EPA’s first proposed deregulatory action to address ongoing DEF problems, this will ease real burdens for operators,” said Zeldin. “The Trump EPA is committed to making trucking safe and reliable again while protecting human health and the environment.”  

“Administrator Zeldin is continuing to deliver for our nation’s farmers, ranchers, and truckers on an issue that has shown the true cost of government overreach. This proposal to eliminate engine deratements and reform the Biden era DEF requirements will lower costs, increase safety, and keep our nation’s food supply moving,” said U.S. Secretary of Agriculture Brooke L. Rollins. “Our rural communities rely on diesel powered engines to deliver their food, families, electricity, and so much more to where it needs to go. The billions in savings will directly benefit those who feed, fuel, and clothe our nation.”  

“The Trump Administration is taking a commonsense approach to alleviating burdensome diesel regulations on behalf of farmers, truckers, and small business owners who were crushed by unworkable environmental activist demands that became costly mandates,” said U.S. Small Business Administrator Administrator Kelly Loeffler. “The EPA, SBA, and USDA have made steady progress toward ending DEF deratements, removing unreliable sensor requirements, and offering operators more practical compliance options. Today’s proposed rule is about locking in long-term reform and delivering a diesel framework that lowers costs, restores equipment reliability, and puts the hardest working Americans first. I am grateful to Administrator Zeldin for his tireless work and partnership on this issue, and for delivering the reform America’s job creators deserve.”