Cold Weather Diesel Reliability Act of 2025

The Cold Weather Diesel Reliability Act would direct the EPA to authorize diesel vehicle manufacturers to suspend automatic engine shutdown and power reduction functions in prolonged cold weather conditions. Currently, federal emissions regulations require diesel engines to automatically derate (reduce power to 5 mph) or shut down when emissions control systems malfunction, including when diesel exhaust fluid (DEF) freezes in temperatures below 12 degrees Fahrenheit. Proponents argue this creates serious safety risks in cold and rural regions, where stranded vehicles in extreme cold can threaten driver safety and disrupt critical services like emergency response, farming, and commercial transportation.

The bill would provide exemptions from these automatic shutdown requirements for vehicles and equipment operating primarily in cold weather climates, particularly in Alaska, Wyoming, and other rural areas. The legislation maintains that emissions standards would still apply outside of the temporary cold-weather operational mode. The bill has been referred to the Senate Committee on Environment and Public Works, which held hearings on it in March 2026. It has not yet been voted on by the full Senate.