Cold Weather Diesel Reliability Act of 2025

[Congressional Bills 119th Congress]
[From the U.S. Government Publishing Office]
[S. 3135 Introduced in Senate (IS)]

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119th CONGRESS
  1st Session
                                S. 3135

To require the Administrator of the Environmental Protection Agency to 
authorize manufacturers of certain vehicles to suspend engine derate or 
shutdown functions in prolonged cold weather conditions, and for other 
                               purposes.


_______________________________________________________________________


                   IN THE SENATE OF THE UNITED STATES

                            November 6, 2025

  Mr. Sullivan (for himself and Ms. Lummis) introduced the following 
bill; which was read twice and referred to the Committee on Environment 
                            and Public Works

_______________________________________________________________________

                                 A BILL


 
To require the Administrator of the Environmental Protection Agency to 
authorize manufacturers of certain vehicles to suspend engine derate or 
shutdown functions in prolonged cold weather conditions, and for other 
                               purposes.

    Be it enacted by the Senate and House of Representatives of the 
United States of America in Congress assembled,

SECTION 1. SHORT TITLE.

    This Act may be cited as the ``Cold Weather Diesel Reliability Act 
of 2025''.

SEC. 2. FINDINGS.

    Congress finds 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 on a 
        year-round basis;
            (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 (42 U.S.C. 
        7401 et seq.) were never intended to jeopardize human safety or 
        impede critical mobility.

SEC. 3. DEFINITIONS.

    In this Act:
            (1) Administrator.--The term ``Administrator'' means the 
        Administrator of the Environmental Protection Agency.
            (2) Covered manufacturer.--The term ``covered 
        manufacturer'' means 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.
            (3) Covered vehicle.--The term ``covered vehicle'' means an 
        on-highway diesel vehicle or nonroad diesel equipment.

SEC. 4. DIESEL ENGINE EMISSIONS RELIEF IN COLD WEATHER REGIONS.

    (a) Cold Weather Sensor Mitigation Measures.--Not later than 180 
days after the date of enactment of this Act, the Administrator shall 
revise any applicable regulation under the Clean Air Act (42 U.S.C. 
7401 et seq.) that applies to covered vehicles or engines used in 
covered vehicles to authorize covered manufacturers to suspend 
inducement-related engine derate or shutdown functions that are 
triggered by emissions control system faults when ambient temperatures 
are at or below zero degrees Centigrade and to specify that no party 
other than a covered manufacturer shall suspend those inducement-
related derate or shutdown functions, subject to the conditions that--
            (1) the engine returns to normal emission control 
        operation, including inducement enforcement, once ambient 
        temperatures rise above zero degrees Centigrade; and
            (2) continued maximum engine performance when ambient 
        temperatures are at or below zero degrees Centigrade is 
        necessary to prevent occupational danger, equipment failure, or 
        loss of essential transportation functionality in remote areas 
        with limited roadside support or emergency communications 
        access.
    (b) Relief to Regions With Prolonged Freezing Conditions.--
            (1) In general.--Not later than 180 days after the date of 
        enactment of this Act, the Administrator shall revise any 
        applicable regulation under the Clean Air Act (42 U.S.C. 7401 
        et seq.) to grant a year-round exemption from diesel exhaust 
        fluid system requirements any covered vehicle that--
                    (A) is primarily operated north of 59 degrees north 
                latitude, as demonstrated by documentation of 
                commercial operation, domicile location, or maintenance 
                and dispatch records; or
                    (B) encounters operational or logistical conditions 
                characterized by prolonged ambient temperatures that--
                            (i) are below the freezing point of diesel 
                        exhaust fluid; or
                            (ii) otherwise make the use of the diesel 
                        exhaust fluid system impractical.
            (2) Scope of relief.--In carrying out paragraph (1), the 
        Administrator shall grant to a covered vehicle described in 
        subparagraph (A) or (B) of that paragraph an exemption from any 
        requirement to include an engine derate or shutdown function 
        that is triggered by the absence, degradation, malfunction, or 
        fault of a diesel exhaust fluid system, including any 
        associated sensors or electronic control modules.

SEC. 5. RULE OF CONSTRUCTION.

    Nothing in this Act waives compliance with any emissions standard 
under the Clean Air Act (42 U.S.C. 7401 et seq.) outside of--
            (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).
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