“Today, we are … demanding detailed data to hold manufacturers accountable,” EPA Administrator Lee Zeldin says. (Dustin Franz/Bloomberg)
February 3, 2026 2:20 PM, EST
Key Takeaways:
- The data collected will allow EPA to independently evaluate ongoing system failures.
- As of Feb. 2, engine manufacturers have 30 days to provide EPA with data on model years 2016, 2019 and 2023 emissions control products.
- In August, EPA issued guidance for truck manufacturers to revise software in new and existing trucks to prevent engine shutdowns in cases where DEF tanks run dry.
Environmental Protection Agency Administrator Lee Zeldin is asking major diesel engine manufacturers to provide critical data about diesel exhaust fluid system failures to remedy equipment problems for truckers and farmers.
EPA is demanding information from the top 14 on-road and nonroad manufacturers that account for more than 80% of all products used in DEF systems.
“EPA understands this is a massive issue, which is why we have already established common-sense guidance for manufacturers to update DEF systems,” Zeldin announced Feb. 3. …The Trump EPA is committed to ending unnecessary frustrations and days lost on the road and in the field for American farmers and truckers.”
The data collected will allow EPA to independently evaluate ongoing system failures and help inform next steps the agency takes in 2026 regarding DEF.
“As I traveled to all 50 states during my first year as EPA administrator, I heard from truck drivers, farmers and many others rightly complaining about DEF and pleading for a fix,” Zeldin added.
EPA is taking measures to determine potential problems with system parts as it pursues future rulemaking.
“The issue facing farmers, truck drivers and equipment operators remains clear to the agency. Sudden speed losses and shutdowns caused by DEF system failures compromise safety and productivity,” the agency stated. “The Trump EPA’s guidance, which significantly reversed deratements, called on manufacturers to revise DEF system software in existing fleets to prevent these sudden shutdowns and give operators more time to repair faults. EPA recognizes that to improve systems, the product designs and materials for these systems must also be the highest quality possible.”
What Information Is EPA Seeking?
EPA is empowered by the Clean Air Act to force manufacturers to provide information to determine if emission control systems are working adequately. The agency also can investigate how engine manufacturers are fulfilling obligations to identify and fix defects.
As of Feb. 2, engine manufacturers have 30 days to provide EPA with data on model years 2016, 2019 and 2023 emissions control products regarding:
- Failure rates
- Repair information
- Warranty claims
EPA plans to use this information to learn if ongoing DEF system failures are linked “to a specific generation of products.” Failure to meet the deadline can result in penalties.
“Yesterday, EPA issued guidance to manufacturers, making it abundantly clear that under the Clean Air Act, Americans have the right to repair their farm and other nonroad diesel equipment. This guidance will allow farmers to fix broken DEF systems at home or in the fields, saving them time and money, while the agency continues its work on DEF,” the agency concluded.
.@SBAgov estimates EPA’s new DEF guidance will save $727 million annually for farmers alone with additional savings for truckers and other sectors of our economy. https://t.co/s5ky6Uu6RX pic.twitter.com/DVUECCy5vh
— U.S. EPA (@EPA) August 12, 2025
In August, EPA issued guidance for truck manufacturers to revise software in new and existing trucks to prevent engine shutdowns in cases where diesel exhaust fluid tanks run dry, a feature present in most trucks built since the 2010 model year. (That was the year most heavy-duty truck manufacturers introduced selective catalytic reduction emissions systems on their vehicles to comply with then-new nitrogen oxide limits.)
EPA noted it has been meeting with manufacturers to receive progress updates on developing improved software in response to EPA’s guidance.
Transport Topics reporters Eugene Mulero and Keiron Greenhalgh examine the critical trends that will define freight transportation in the year ahead. Tune in above or by going to RoadSigns.ttnews.com.
In addition to the agency’s August 2025 guidance, EPA stated that starting with model year 2027, all new diesel on-road trucks must be engineered to avoid sudden and severe power loss after running out of DEF.
“Under the Trump EPA’s August guidance, major changes were undertaken. Heavy-duty trucks now should only receive a warning light for 650 miles or 10 hours after a fault is detected. Following that time, the engine will only mildly derate, allowing trucks to operate normally and without speed limits for up to 4,200 miles or two work weeks. Only after about four work weeks does speed drop to 25 mph until repairs are made. Nonroad equipment has no impacts for the first 36 hours before a slight torque reduction then takes effect,” according to EPA.
The agency noted it “has consistently encouraged manufacturers to provide the relief as quickly as possible.”
