Trump Administration Announces Latest Action to Address Diesel Exhaust Fluid (DEF) System Complaints, Saves American Farmers and Truckers Over $13 Billion Annually
EPA Removes DEF Sensor Requirements Saving Americans Billions Annually and Countless Hours of Lost Time and Productivity
WASHINGTON – Today, at the White House Great American Agriculture Celebration, President Trump announced another decisive action U.S. Environmental Protection Agency (EPA) Administrator Lee Zeldin has taken to address nationwide concerns from farmers, truckers, motor coach operators, and other diesel equipment operators regarding Diesel Exhaust Fluid (DEF) system failures by removing the DEF sensor requirement for all diesel equipment. EPA understands that sudden speed losses and shutdowns caused by DEF system failures that compromise safety and productivity are unacceptable and problematic. While EPA continues to pursue all legal avenues to address Americans’ complaints, today the agency is implementing another part of Administrator Zeldin’s plan to help keep American operators from losing days in the field or on the road because of faulty DEF systems. EPA’s new guidance, which removes DEF sensors, will provide immediate relief and save billions of dollars in repairs and lost productivity. According to the U.S. Small Business Administration (SBA), this guidance will save farmers $4.4 billion a year and this action will provide $13.79 billion a year of savings to Americans.
On February 3, 2026, EPA demanded critical data on DEF system failures from the manufacturers that account for over 80 percent of all products used in DEF systems. This information will arm EPA with what it needs to permanently address DEF system failures. Thus far, the agency has received data from 11 of the 14 manufacturers, and in less than a month, EPA has turned around preliminary findings to issue today’s guidance demonstrating Administrator Zeldin’s commitment to fixing this issue.
“Failing DEF systems are not an east coast or west coast or heartland issue; it is a nationwide disaster. I have heard from truck drivers, farmers, and many others complaining about DEF and pleading for a fix in all 50 states I visited during my first year as EPA Administrator,” said EPA Administrator Zeldin. “Americans are justified in being fed up with failing DEF system issues. EPA understands this is a massive issue and has been doing everything in our statutory power to address this. Today, we take another step in furthering our work by removing DEF sensors. Farmers and truckers should not be losing billions of dollars because of repair costs or days lost on the job.”
“Since joining the Trump Administration, I have worked hand in glove with Administrator Zeldin and consumers who have been hampered by faulty Diesel Exhaust Fluid systems. Through this partnership, we have seen historic actions taken to rectify the problems everyday Americans are facing in their trucks and non-road equipment,” said U.S. Secretary of Agriculture Brooke L. Rollins. “I’m proud to see the EPA responding to the demands of these consumers and working to implement real change to solve these issues. The action today will allow engine manufacturers to update their systems to monitor the pollutants we are targeting rather than the Diesel Exhaust Fluid itself which has caused many of the system failures. This powerful step will provide much needed relief, but we will continue to work towards a solution that protects the environment while eliminating damages to farmers and truckers nationwide.”
“Few small businesses have been hit harder by the Green New Scam than those who make up America’s great agriculture industry, where massive regulatory burdens have crushed family farms and driven up grocery costs,” said SBA Administrator Kelly Loeffler. “Today, by eliminating DEF mandates, the Trump Administration is taking yet another step to free up hardworking Americans to focus on the vital work of feeding, clothing, building, and fueling our nation. I applaud Administrator Zeldin for his leadership on this issue, and I look forward to our continued collaboration to cut red tape for small businesses across the U.S. food supply chain.”
The preliminary review of the warranty data suggests that DEF sensor failures are a significant source of warranty claims and DEF-related inducement. Farmers and truck drivers should not have their vehicles stop working because a sensor isn’t working properly. EPA is taking immediate action on this new information. The agency’s new guidance makes clear that under existing regulations, manufacturers can stop inaccurate DEF system failures by removing traditional emission sensors, known as Urea Quality Sensors, and switching to nitrous oxide (NOx) sensors.
EPA also affirms that approved NOx sensor-based software updates can be installed on existing engines without being treated as illegal tampering under the Clean Air Act. This is in line with EPA’s February 2026 Right to Repair clarification guidance, which removed a major barrier keeping farmers from fixing their faulty DEF systems in the field. EPA anticipates the switch will greatly curb errors that traditional sensor technologies have been prone to and reduce the issues Americans face with inaccurate DEF failures.
Since the start of the Trump administration, EPA has prioritized the farming community by advancing commonsense policies and issuing clear guidance to improve operational reliability. In August 2025, EPA issued new, clear guidance calling on engine and equipment manufacturers to revise DEF system software in existing vehicles and equipment to massively reverse deratements that harm farmers and truckers. In response to this guidance, manufacturers have started making this new and improved software available to Americans in some existing vehicles and will be extending the improvements to owners of older equipment. In the near future, EPA will also be issuing a new deregulatory proposal that will completely remove all DEF deratements for new vehicles and engines. With these changes, sudden speed losses, which compromise safety and productivity, will be an issue of the past.
Additionally, EPA will continue reviewing data collected from manufacturers and use this information to identify opportunities to improve the emission systems for the American people beyond the actions taken to date. Given the breadth of EPA’s data request, some of the largest manufacturers required additional time to compile and submit their data. EPA will give the public a complete assessment of the data collected once all data is received.
Today’s announcement does not weaken or remove emissions standards. Instead, it ensures that those standards are met in a way that actually works in the real world. EPA remains committed to protecting human health and the environment while ensuring that the Americans who feed, clothe, and power our economy are not burdened by unnecessary system failures.
For more information, please see EPA’s Diesel Exhaust Fluid.
Background
Since 2010, most on-road diesel trucks and many types of nonroad equipment (such as tractors and construction machinery) have used selective catalytic reduction systems that inject DEF into exhaust streams to reduce NOx emissions.
Prior to EPA’s August 2025 guidance, when DEF ran out or there was an unexpected mechanical failure, systems forced a vehicle to drastically reduce speed or become inoperable. In many cases, vehicles were limited to as little as five miles per hour within hours of a DEF-related fault. This caused needless frustration, operational delays, and real economic hardship for operators. Under the Trump EPA’s August 2025 guidance, major changes were undertaken. Heavy-duty trucks should now 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 the speed drop to 25 mph until repairs are made. Nonroad equipment has no impact for the first 36 hours before a slight torque reduction then takes effect.
In addition to EPA’s August 2025 guidance, EPA announced sweeping changes so that starting with MY 2027, all new diesel on-road trucks must be engineered to avoid sudden and severe power loss after running out of DEF.