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Story summary
- The U.S. Environmental Protection Agency announced measures addressing Diesel Exhaust Fluid (DEF) system failures in heavy-duty diesel vehicles.
- Administrator Lee Zeldin said the EPA is demanding data from manufacturers on warranty claims and failure rates for specific model years.
- This follows August 2025 guidance to reduce derates when DEF levels are low.
- The EPA will assess whether these derates are necessary and monitor outcomes.
