Cold Weather Diesel Reliability Act of 2025

This bill mandates the Environmental Protection Agency (EPA) to implement new regulations providing relief for diesel vehicles operating in cold weather. Its primary purpose is to ensure the reliability and safety of critical diesel transportation and equipment by addressing issues related to emissions control systems in freezing temperatures. The legislation aims to prevent automatic engine shutdowns or power reductions that could pose significant risks in remote, cold environments. Specifically, the Administrator must authorize covered manufacturers to temporarily suspend engine derate or shutdown functions triggered by emissions control system faults when ambient temperatures are at or below zero degrees Celsius. This suspension is permitted only if necessary to prevent occupational danger, equipment failure, or loss of essential transportation functionality in remote areas, with normal emission control resuming above freezing. Additionally, the bill requires a year-round exemption from diesel exhaust fluid (DEF) system requirements for vehicles primarily operated north of 59 degrees north latitude or in regions experiencing prolonged temperatures below the DEF freezing point. This exemption specifically covers derate or shutdown functions caused by DEF system issues, ensuring continued operation. The legislation clarifies that these provisions do not waive compliance with Clean Air Act emissions standards outside of these defined cold-weather operational modes and exemptions.