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HR 9618

DEF Act

119th Congress Introduced by Jack Bergman and 4 co-sponsors

The DEF Act creates a 10-year window of regulatory stability, blocking stricter near-term emission rules for on-road and nonroad engines while allowing guidance-based updates.

Introduced in House
0
WeVote Research Nonpartisan
Bill Summary · HR 9618

DEF Act (H.R. 9618) – Summary

Purpose and intent

  • The bill, titled the Diesel Engine Flexibility Act (DEF Act), amends the Clean Air Act to preserve regulatory stability for motor vehicles, motor vehicle engines, nonroad vehicles, and nonroad engines.
  • Its overarching aim is to limit the pace and stringency of new emission standards for on-road and nonroad powertrains in the near term, while still allowing certain actions aligned with specific guidance documents.

Key provisions

On-road vehicles and engines (Section 202, new subsection (n))

  • Establishes a 10-year preservation window starting from enactment.
  • Guided by a set of “covered guidance documents,” implementation of certain strategies and monitoring related to diesel exhaust fluids (DEF) and SCR technology, for vehicles and engines meeting 2007 or 2010 standards, shall not be a prohibited act if done consistent with the guidance and existing certification and useful life rules.
  • Temporary regulatory stability:
    • During the 10-year window, the Administrator may not promulgate or tighten regulations under this title or Section 209(b that are more stringent than the 2007 or 2010 standards, with key exceptions:
    • Approving software updates, repair strategies, diagnostic improvements, or monitoring approaches aligned with covered guidance.
    • Enforcing anti-defeat and anti-tampering measures.
    • Implementing recalls, defect reporting, certification, warranty or other administrative requirements that do not impose stricter emission standards or higher compliance obligations.
    • Approving voluntary manufacturer actions that keep compliant with certification and life requirements.
  • Lead time after the window:
    • Any new or revised standard post-window must apply for at least 3 model years and take effect no earlier than five model years after promulgation.

  • Required considerations for post-window standards:

    • Minimize operational disruption, derates, shutdowns.
    • Preserve durability and aftertreatment system integrity (SCR, DPF).
    • Effects on resale value, financing, inventories, and equipment availability.
    • Costs to owners/operators (downtime, repairs, logistics, replacements).
    • Need for national consistency and cross-category harmonization.

  • Rule of construction:

    • No permanent disablement of emissions control systems.
    • No exemption from other emission standards.
    • Permit software updates and monitoring approaches that conform to applicable requirements.

  • Definitions provided:

    • 2007 and 2010 standards are tied to specific CFR provisions as of Jan 1, 2025.
    • Covered guidance documents include:
    • Revised Guidance for Light Duty Vehicles, Heavy-Duty Diesel Engines and Nonroad Compression-Ignition Engines Using SCR (IACD–2025–10, Aug 11, 2025).
    • DEF Quality Monitoring Using Alternate Sensor Technologies (IACD–2026–05, Mar 26, 2026).

Nonroad vehicles and nonroad engines (Section 213, new subsection (e))

  • Establishes a parallel 10-year preservation framework:
    • Guidance-based safe harbor for DEF-related and monitoring strategies for nonroad equipment meeting Tier 4 standards.
    • Temporary regulatory stability within 10 years, prohibiting stricter standards than Tier 4, with exceptions mirroring on-road allowances:
    • Software updates, repair strategies, diagnostics, monitoring approaches aligned with covered guidance.
    • Enforcement against defeat devices and tampering.
    • Recalls and administrative requirements not increasing stringency.
    • Voluntary manufacturer actions maintaining compliance with certification and useful life requirements.
    • Lead time after the window: any Tier 4-related standard or requirement must apply for at least 3 model years and take effect no earlier than five model years after promulgation.
    • Post-window considerations similar to on-road provisions (operational disruption, durability, resale/value, costs, national consistency, and harmonization).
  • Definitions mirror the on-road section, including covered guidance documents (with additional guidance: Clarification Regarding Temporarily Disabling Aspects of an Emission Control System for Nonroad Engines, Jan 30, 2026, IACD–2026–01).

Affected parties

  • On-road: Manufacturers of light- and heavy-duty vehicles and engines, including heavy-duty engines/vehicles and light-duty engines/vehicles/trucks, plus owners and operators of these vehicles.
  • Nonroad: Manufacturers and operators of nonroad vehicles and engines (e.g., construction, agricultural, and other equipment with Tier 4-compliant engines).

Procedural and timeline aspects

  • The bill sets a 10-year period of regulatory stability from enactment for both on-road and nonroad sectors, during which standards cannot be made more stringent than the 2007/2010 (on-road) or Tier 4 (nonroad) standards.
  • After the 10-year window, new or revised standards must:
    • Apply for at least 3 model years.
    • Take effect no earlier than five model years after promulgation.
  • It defines specific “covered guidance documents” that guide what counts as permissible actions during the stability period.
  • The act explicitly preserves the ability to approve software updates, recall actions, defect reporting, and voluntary manufacturer actions, as long as they do not impose stricter standards or materially increase obligations.

Sponsors and status

  • Introduced in the House on July 9, 2026, by Rep. Julie Fedorchak (with co-sponsors: Don Davis, Brad Finstad, Michelle Fischbach, Jack Bergman).
  • Referred to the House Committee on Energy and Commerce.

Potential impact

  • Aims to provide regulatory predictability for vehicle and engine manufacturers and owners by limiting near-term tightening of emission standards.
  • Could slow the pace of more stringent future emissions requirements and shift emphasis to implementing and verifying the effects of existing standards and approved guidance.
  • Seeks to balance environmental objectives with concerns about operational disruption, durability of aftertreatment systems, resale value, and cost to consumers and businesses.

Compiled from official sources — confirm details with the bill’s official record.

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