The Environmental Protection Agency is requiring 14 major diesel engine manufacturers to provide detailed information about diesel exhaust fluid system failures that have affected farmers and truckers nationwide.
EPA Administrator Lee Zeldin announced the agency will collect data on warranty claims, failure rates, and repairs for model years 2016, 2019 and 2023. The manufacturers, which represent over 80% of DEF system products, have 30 days to comply or face potential penalties.
"Today, we are furthering that work and demanding detailed data to hold manufacturers accountable for the continued system failures," Zeldin said. "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 move follows EPA guidance issued in August 2025 to address sudden losses in speed caused by DEF malfunctions. Previously, vehicles could be limited to five miles per hour within hours of a system fault. Under the guidance, trucks are supposed to receive 650 miles of warning time before mild performance reductions.
DEF systems inject fluid into exhaust streams to reduce nitrogen oxide emissions and have been required on most diesel trucks since 2010. However, unexpected failures have caused widespread frustration, with sudden speed losses that compromise safety and productivity.
