ICYMI: Administrator Zeldin Takes Additional Measures to Address Diesel Exhaust Fluid (DEF) Issues for American Farmers and Truckers

ICYMI: Administrator Zeldin Takes Additional Measures to Address Diesel Exhaust Fluid (DEF) Issues for American Farmers and Truckers

February 6, 2026

WASHINGTON - On Tuesday, February 3, 2026, Administrator Lee Zeldin took another step to further the Trump EPA's work to address widespread concernsExit EPA's website from farmers, truckers, motor coach operators, and other diesel equipment operators regarding Diesel Exhaust Fluid (DEF) system failures. This announcement is a follow up to the August 2025 guidanceExit EPA's website reversing deratements that were harming farmers and truckers, and EPA is pursuing rulemaking opportunities to provide additional relief for Americans. EPA is demanding information from major diesel engine manufacturers on critical data from DEF system failures and the data collected will allow EPA to independently evaluate ongoing system failures to help inform next steps the agency takes in 2026 pertaining to DEF.

Read coverage below on this major achievement for farmers and truckers.

AgWeb: More DEF Relief? EPA Takes New Action for Farmers and Truckers Exit EPA's website

"On the heels of clarifying farmers' right to repair their own equipment, EPA is escalating pressure on diesel engine manufacturers over ongoing Diesel Exhaust Fluid (DEF) system failures the administration claims continue to sideline farm machinery and trucks. . .The move builds directly on Monday's EPA right-to-repair guidance announcement that clarified the Clean Air Act does not prohibit farmers from fixing their own non-road diesel equipment, which includes making temporary emissions overrides when necessary to complete repairs."

Morning Ag Clips: EPA Measures Aim to Address Diesel Exhaust Fluid (DEF) Issues for Farmers Exit EPA's website

"Today [Feb. 3, 2026], U.S. Environmental Protection Agency (EPA) Administrator Lee Zeldin took another step to further the Trump EPA's work to address widespread concerns from farmers, truckers, motor coach operators, and other diesel equipment operators regarding Diesel Exhaust Fluid (DEF) system failures."

Heavy Duty Trucking: EPA Wants to Know: Are DEF De-Rates Really Needed for Diesel Emissions Compliance?Exit EPA's website Exit EPA's website

". . . The move is a follow-up to the EPA's guidance last August to address the frustration experienced by truckers when DEF system failures result in sudden speed losses and shutdowns. That guidance called on manufacturers to revise DEF system software in existing fleets to prevent these sudden shutdowns and give operators more time to repair faults."

CDLLIFE: EPA promises truckers more relief for Diesel Exhaust Fluid system-related sudden speed losses and shutdowns Exit EPA's website

"'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. EPA understands this is a massive issue, which is why we have already established commonsense guidance for manufacturers to update DEF systems,' said Zeldin."

Transport Topics: EPA Gives Engine Makers 30 Days to Provide DEF System DataExit EPA's website

"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."

Progressive Farmer: DEF System Failures Under EPA ScrutinyExit EPA's website

"The U.S. Environmental Protection Agency is giving diesel equipment manufacturers 30 days to submit information to determine whether ongoing diesel exhaust fluid, or DEF, system failures are related to specific model years. This is a first step to potentially creating rules to further prevent sudden speed and power losses."

Overdrive: EPA looks to permanently end diesel derates due to DEF, aftertreatment problems Exit EPA's website

"'As part of that regulatory process to hopefully be able to PERMANENTLY eliminate the deratements ENTIRELY, I am sending a mandatory data collection request today to manufacturers regarding DEF system failures to quickly evaluate ongoing issues independently and launch the next step Americans are DEMANDING,' EPA Administrator Lee Zeldin wrote on Twitter. 'On behalf of our nation's truckers, farmers, and others, WE ARE GOING TO GET THIS DONE at TRUMP SPEED!'"

Pick Up Truck Talk: EPA Moves to Force Engine Makers to Fix Notoriously Faulty Diesel DEF Systems, Citing Major Savings for Farmers Exit EPA's website

"The U.S. Environmental Protection Agency is ramping up its pressure on engine makers to fix persistent diesel exhaust fluid (DEF) system failures that have disrupted farming, trucking, and heavy-equipment operations nationwide. . . 'Today, we are furthering that work and demanding detailed data to hold manufacturers accountable for the continued system failures [Zeldin said in a press release]. 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 Fast Lane Truck: EPA Announces New Measures to Eliminate Low DEF Limp Mode for Diesel Trucks, Advance DEF Right-to-Repair Exit EPA's website

"We've heard several complaints over the years from truck owners regarding DEF systems, and some of the guys have experienced issues firsthand with their own modern trucks (see below). This new plan could change things long-term for truck owners - particularly if they don't have to contend with deratements for running out of DEF, and aren't forced to refill the system to get the maximum performance from their trucks."

Freight Waves: EPA Targets Truck Engine Makers On DEF System FailuresExit EPA's website

"In a move to end 'limp mode' nightmares for truckers, Environmental Protection Agency Administrator Lee Zeldin announced on Tuesday that the agency is launching a formal investigation into the reliability of Diesel Exhaust Fluid (DEF) systems. . . EPA is demanding that the top 14 diesel engine manufacturers - representing 80% of the market - hand over internal data on warranty claims and engine failure rates, with the goal of determining why DEF systems often fail and to hold manufacturers accountable for hardware that can leave trucks stranded. The information will be used as the basis for a future rulemaking."

GMA Authority: EPA To Investigate Diesel Engine DEF System FailuresExit EPA's website

". . . In an announcement earlier this week, EPA Administrator Lee Zeldin said the agency is now demanding detailed information from manufacturers in order 'to independently evaluate ongoing system failures and help inform next steps the agency takes in 2026 pertaining to DEF.' The effort builds on guidance issued in over the summer that aimed at curbing systems that cause vehicles to enter 'limp mode' when DEF levels are low."

The Autopian: The U.S. Considers No Longer Requiring Limp Mode For Running A Diesel Truck Low On DEFExit EPA's website

". . . EPA Administrator Lee Zeldin has spent part of his tenure making deregulation a focus of the department. One area of EPA deregulation has been easing rules for what should happen when a truck either runs out of Diesel Exhaust Fluid or the DEF equipment otherwise fails. EPA Administrator Lee Zeldin had previously ordered truck makers to stop forcing trucks into immediate limp modes due to low DEF. Now, as first pointed out by the Drive, the EPA is considering eliminating the requirement for limp mode entirely."

The Trucker: EPA takes additional measures to address DEF issues for farmers and truckersExit EPA's website

"'The agency is committed to working with manufacturers to ensure practical, durable solutions that simultaneously support emissions reductions and reliable operations,' EPA said. 'EPA has been meeting with manufacturers to receive updates on their progress in developing improved software in response to EPA's guidance. The agency has consistently encouraged manufacturers to provide the relief as quickly as possible.'"

Land Line Media: EPA doubles down on DEF overhaul, demands data from manufacturersExit EPA's website

"'On the heels of EPA's Final Rule last week restricting CARB's authority on trucks registered outside of California, OOIDA applauds the agency's willingness to give truckers more flexibility when dealing with faulty emissions systems,' OOIDA President Todd Spencer said. 'We believe the forthcoming data from engine manufacturers will once again prove that problems with nonsensical DEF regulations have sidelined small-business truckers for too long. We look forward to continued engagement with Administrator Zeldin and his staff to implement additional emissions solutions that better reflect the realities of trucking.'"