119 S3135 IS: Cold Weather Diesel Reliability Act of 2025
U.S. Senate
2025-11-06
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II
119th CONGRESS
1st Session
S. 3135
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.
1.

Short title
This Act may be cited as the “Cold Weather Diesel Reliability Act of 2025”.
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.
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.
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.
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).