Overview
- New guidance directs manufacturers to engineer model-year 2027 and later heavy-duty trucks to avoid abrupt power loss when diesel exhaust fluid is depleted.
- Under Section 208(a), the EPA is requiring the top 14 on-road and nonroad diesel makers to submit warranty, failure-rate, and repair data for model years 2016, 2019, and 2023 within 30 days or face potential penalties.
- The agency is preparing a proposal to reconsider the 2022 Heavy-Duty Engine and Vehicle NOx rule as it evaluates whether derates remain necessary for compliance.
- Earlier guidance from August 2025 set staged responses for MY2027 trucks, including extended warning and mild derate periods before any stringent speed governors take effect.
- Separate guidance affirms that owners may repair DEF systems on farm and other nonroad diesel equipment under the Clean Air Act.