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Legislation tracker

The DEF Act: H.R. 9618 Tracker

Tracking the Diesel Engine Flexibility Act — a 10-year safe harbor for EPA DEF derate relief guidance and a 10-year freeze of heavy-duty emissions standards at the 2007/2010 levels.

Bill status

H.R. 9618 · 119th Congress

DEF Act / Diesel Engine Flexibility Act

Sponsor
Rep. Julie Fedorchak (R-N.D.)
Co-sponsor
Rep. Don Davis (D-N.C.)
Current status
Forwarded to full House Energy and Commerce Committee by voice vote, July 14, 2026
  1. Step 1IntroducedComplete
  2. Step 2SubcommitteeComplete
  3. Step 3Full Committee
  4. Step 4House Floor
  5. Step 5Senate
  6. Step 6Signed

Status as of July 14, 2026

Plain-English summary

What the bill does

The DEF Act locks the EPA’s 2025–2026 DEF derate relief guidance into a 10-year legal safe harbor for manufacturers, fleets, and independent technicians who follow it.

It also freezes heavy-duty on-road emissions standards at the 2007/2010 levels (Tier 4 for nonroad) for the same 10 years, including blocking California waivers under Sections 209(b) and 209(e)(2) of the Clean Air Act.

The two halves

Safe harbor and freeze

The Safe Harbor

Protects manufacturers, fleets, and independent technicians who follow EPA guidance documents IACD-2025-10, IACD-2026-01, and IACD-2026-05 from Clean Air Act prohibited-act liability for 10 years.

The Freeze

EPA may not promulgate, revise, authorize, or implement anything more stringent than the 2007/2010 on-road standards or Tier 4 nonroad for 10 years. Effectively suspends the 2027 low-NOx rule and blocks CARB waivers. After the freeze, any new standard needs 5 years of lead time and 3 model years of stability.

What it means

By affected group

Truckers / Fleets

2027 rule suspended. Derate schedules stay at 650 miles / 10 hours warning, then mild derate, then 25 mph after about four work weeks. No pre-buy scramble.

Farmers / Nonroad

36-hour no-impact window after a DEF fault. Repair overrides protected. Tier 5 blocked for a decade.

Passenger Carriers

Motorcoaches run the same engines. Derate relief on a loaded coach is a passenger-safety issue, not just an operator convenience.

Clarifications

What it does NOT do

  • No deletes.
  • No permanent disablement of emissions systems.
  • Defeat-device and tampering enforcement continues.
  • Recalls and warranties continue.
  • Existing 2007/2010 on-road and Tier 4 nonroad standards stay fully in force.

Timeline

Key dates

  1. Aug. 11, 2025
    EPA derate guidance issued

    IACD-2025-10 — heavy-duty DEF inducement / derate relief guidance.

  2. Jan. 30, 2026
    Nonroad repair guidance issued

    IACD-2026-01 — nonroad repair-window guidance protecting Tier 4 diagnostic overrides.

  3. March 26, 2026
    DEF quality sensor guidance issued

    IACD-2026-05 — DEF quality-sensor fault handling.

  4. July 9, 2026
    Bill introduced

    H.R. 9618 introduced in the House.

  5. July 14, 2026
    Subcommittee voice vote

    Forwarded to full House Energy and Commerce Committee.