Cold Weather Diesel Reliability Act of 2025

The Cold Weather Diesel Reliability Act of 2025 requires the Environmental Protection Agency (EPA) to revise Clean Air Act regulations to address diesel vehicle challenges in extreme cold. It allows diesel vehicle manufacturers to temporarily disable engine power reductions or shutdowns caused by emissions system faults when temperatures are at or below freezing, but only until temperatures rise above freezing. The bill also grants a year-round exemption from diesel exhaust fluid (DEF) system requirements for vehicles primarily operating north of 59°N latitude or in regions with prolonged freezing conditions that make DEF use impractical. This exemption prevents engine derates or shutdowns due to DEF system issues, ensuring critical transportation and emergency services remain functional. The bill does not change overall emissions standards but provides targeted relief for safety and operational needs in cold weather regions.