S3135119th CongressWALLET

Cold Weather Diesel Reliability Act of 2025

Sponsored By: Senator Dan Sullivan

Introduced

Summary

This bill would temporarily allow diesel vehicles to bypass cold‑weather emissions shutdowns to keep engines running and preserve safety and mobility in extreme cold. It would let manufacturers suspend engine derates or shutdowns when ambient temperatures are at or below 0 degrees Centigrade and provide a year‑round exemption from diesel exhaust fluid requirements for vehicles that operate primarily north of 59 degrees north latitude or that face prolonged freezing conditions.

Show full summary
  • Drivers and emergency responders: Keeps engines at full power in extreme cold so trucks and equipment are less likely to shut down unexpectedly, reducing the risk of being stranded during critical missions.
  • Rural and remote communities: Supports continued deliveries, utility work, and winter operations where diesel exhaust fluid storage and supply are unreliable.
  • Manufacturers: Allows covered manufacturers to suspend inducement-related derates or shutdown functions tied to DEF system faults in the defined cold conditions and to claim the year‑round DEF exemption for qualifying vehicles.
  • Regulators and air quality: Limits relief to narrowly defined cold conditions and preserves existing emission standards outside those modes, so normal emissions rules remain in effect when vehicles are not operating under the cold exceptions.

Bill Overview

Analyzed Economic Effects

3 provisions identified: 2 benefits, 0 costs, 1 mixed.

Emissions standards remain mostly intact

If enacted, the bill would make clear that existing emissions standards stay in force. Only two narrow exceptions would be allowed: the cold-weather derate pause at or below 0°C and the DEF exemption for vehicles mainly used north of 59°N or in prolonged freezing. Outside those narrow limits, compliance with emissions rules would still be required.

Year-round DEF exemption for northern use

If enacted, within 180 days the EPA would allow a year-round exemption from diesel exhaust fluid (DEF) requirements for covered vehicles. The exemption would apply if a vehicle is mainly used north of 59°N or regularly faces prolonged freezing that makes DEF impractical. Vehicles with the exemption would not need derates or shutdowns triggered by DEF faults. This could reduce downtime for affected operators but may affect local air quality.

Cold-weather engine derate relief

If enacted, within 180 days the EPA would allow manufacturers to pause engine derates or shutdowns when temperatures are at or below 0°C. Only the manufacturer could pause the derate. Engines would return to normal emissions controls once temperatures rise above 0°C. The pause would only apply when needed to avoid danger, equipment failure, or loss of essential transport in remote areas.

Sponsors & CoSponsors

Sponsor

Dan Sullivan

AK • R

Cosponsors

  • Cynthia Lummis

    WY • R

    Sponsored 11/6/2025

  • John Curtis

    UT • R

    Sponsored 2/26/2026

Roll Call Votes

No roll call votes available for this bill.

View on Congress.gov

Related Bills

Back to Legislation

Take It Personal

Get Your Personalized Policy View

Create a free account to save research, track policy impacts, and unlock your personalized versions of these pages.

Already have an account? Sign in