EPA Administrator Zeldin travels to Iowa, reveals fresh EPA DEF guidelines, attends State Fair, commemorates One Big Beautiful Bill
In a significant move aimed at enhancing productivity and safety, the U.S. Environmental Protection Agency (EPA) has issued new guidance for Diesel Exhaust Fluid (DEF) systems. This guidance is designed to prevent sudden engine shutdowns and power losses caused by DEF-related faults, providing operators with more time to diagnose and repair issues before severe derates or shutdowns occur.
The new EPA guidance requires engine and equipment manufacturers to revise DEF system software on existing diesel vehicles equipped with selective catalytic reduction (SCR) systems. This revision is expected to bring about a number of key changes, including the relaxation of strict inducement requirements and the requirement for manufacturers to update software in current vehicles to prevent immediate severe slowdowns or shutdowns due to DEF faults.
Starting with model year 2027, new diesel trucks must be designed to avoid sudden and severe power loss after running out of DEF. This measure is expected to benefit operators by providing them with earlier fault warnings and extended time to address issues, thus enabling them to continue working without abrupt interruptions or safety hazards.
The EPA's guidance balances maintaining environmental standards for nitrogen oxide emissions (via DEF reducing NOx), while improving operational reliability and user experience by eliminating sudden derates that have caused costly productivity losses, especially affecting farmers, truckers, and construction operators.
On August 12, 2025, U.S. EPA Administrator Lee Zeldin was in Iowa where he discussed these developments. Administrator Zeldin was joined by U.S. Small Business Administration (SBA) Administrator Kelly Loeffler, U.S. Department of Agriculture (USDA) Secretary Brooke L. Rollings, Iowa Governor Kim Reynolds, Senator Joni Ernst (R-IA), and U.S. Representative Randy Feenstra (IA-4). The group attended the Iowa State Fair and served as grill masters at the Iowa Pork Producers Association tent.
During his trip, Administrator Zeldin emphasized investing in Artificial Intelligence (AI) and streamlined permitting as part of President Trump's One Big Beautiful Bill (OBBB). He also prioritized baseload power to unleash American energy dominance as a key aspect of the OBBB.
Administrator Zeldin and Administrator Loeffler also spoke on a panel with Senator Ernst at the Ernst Entrepreneur Expo at Iowa State University in Ames, Iowa. The event marked a celebration of the victories that President Trump's OBBB will deliver for hardworking Iowans. Administrator Zeldin concluded his trip at a One Big Beautiful Bill Celebration at Mid-States Companies in Nevada, Iowa.
[1] EPA's Guidance on Diesel Exhaust Fluid (DEF) System Software Revision: https://www.epa.gov/diesel-exhaust-fluid-def-system-software-revision [2] EPA's Guidance for Engine and Equipment Manufacturers: https://www.epa.gov/engines-vehicles-and-air-pollution/guidance-engine-and-equipment-manufacturers [3] EPA's New Guidance for Diesel Trucks: https://www.epa.gov/newsreleases/epa-issues-new-guidance-diesel-trucks-prevent-sudden-engine-shutdowns [4] EPA's Guidance for Diesel Vehicles: https://www.epa.gov/cleandiesel/epas-guidance-diesel-vehicles-equipped-selective-catalytic-reduction-scr-systems [5] EPA's Guidance for DEF System Faults: https://www.epa.gov/cleandiesel/epas-guidance-def-system-faults-and-sudden-engine-shutdowns
- The Environmental Protection Agency (EPA) has steered towards promoting productivity and safety with new guidance on Diesel Exhaust Fluid (DEF) systems.
- This new guidance aims to thwart sudden engine shutdowns and power losses caused by DEF-related faults, allowing operators ample time to diagnose and rectify issues before severe derates or shutdowns take place.
- The EPA's guidance requires engine and equipment manufacturers to revise DEF system software in existing diesel vehicles equipped with selective catalytic reduction (SCR) systems, bringing about changes like a relaxation of strict inducement requirements.
- With the new EPA guidance, model year 2027 diesel trucks will be designed to avert sudden and severe power loss after DEF depletion, benefiting operators with early fault warnings and extended time to resolve issues.
- The EPA's DEF system guidance upholds environmental standards for nitrogen oxide emissions while improving operational reliability and user experience by eradicating sudden derates that have led to costly productivity losses, particularly affecting farmers, truckers, and construction operators.
- On August 12, 2025, EPA Administrator Lee Zeldin was in Iowa where he discussed these developments alongside other officials, emphasizing investing in Artificial Intelligence (AI) and streamlined permitting as part of President Trump's One Big Beautiful Bill (OBBB).
- Administrator Zeldin and Administrator Kelly Loeffler also addressed the Ernst Entrepreneur Expo at Iowa State University in Ames, Iowa, highlighting the benefits of President Trump's OBBB for Iowa's working class.
- Sources like [1], [2], [3], [4], and [5] offer extensive information on the EPA's guidance for DEF system software revision, engine and equipment manufacturers, new guidelines for diesel trucks, diesel vehicles equipped with SCR systems, and DEF system faults and sudden engine shutdowns.
