Overview

• At the Iowa State Fair, Administrator Lee Zeldin called software-imposed limp mode “unnecessary” and pledged to revise regulations after farmers and small businesses reported costly shutdowns
• Starting with model-year 2027, the EPA will bar new on-road diesel trucks from being engineered to force instant power loss when diesel exhaust fluid runs out
• The agency plans to work with truck and engine manufacturers on guidance to retrofit existing diesel vehicles’ software to comply with the updated policy
• Under the revised standards, diesel systems must allow at least 4,200 miles or 80 operational hours before initiating any DEF-related power reduction
• Environmental analysts warn that removing limp-mode enforcement could encourage extended operation without DEF and lead to higher nitrogen oxide emissions