S. 3135 — Cold Weather Diesel Reliability Act of 2025

This section sets forth congressional findings that (1) diesel vehicles are vital for critical transportation and emergency services in cold weather regions; (2) in rural regions with prolonged freezing conditions, diesel exhaust fluid storage, supply, and system functionality are frequently unreliable and logistically impractical year-round; (3) automatic engine shutdowns and power reductions due to emissions control malfunctions in extreme cold pose serious, life-threatening risks; and (4) emissions safeguards under the Clean Air Act were never intended to jeopardize human safety or impede critical mobility.

This section establishes definitions for purposes of the Act, including (1) Administrator, as the Administrator of the Environmental Protection Agency; (2) covered manufacturer, as the manufacturer (as defined in section 216 of the Clean Air Act, 42 U.S.C. 7550) of a covered vehicle or an engine of a covered vehicle; and (3) covered vehicle, as an on-highway diesel vehicle or nonroad diesel equipment.

This section directs the EPA Administrator, not later than 180 days after enactment, to revise Clean Air Act regulations to (1) authorize covered manufacturers to suspend inducement-related engine derate or shutdown functions triggered by emissions control system faults for covered vehicles or engines when ambient temperatures are at or below 0 degrees Centigrade—provided the engine returns to normal operation above that temperature and continued performance is necessary to prevent occupational danger, equipment failure, or loss of essential transportation in remote areas—while prohibiting any other party from suspending those functions; and (2) grant year-round exemptions from diesel exhaust fluid system requirements, including associated derate or shutdown functions, for covered vehicles primarily operated north of 59 degrees north latitude or in prolonged freezing conditions that make such systems impractical.

This section provides that nothing in this Act waives compliance with any emissions standard under the Clean Air Act except for (1) the temporary cold-weather operational mode authorized under section 4(a); and (2) the exemption from diesel exhaust fluid system requirements under section 4(b).