The Diesel Engine Flexibility Act (DEF Act) amends the Clean Air Act to freeze vehicle and engine emission regulations for ten years, preventing the Environmental Protection Agency from adopting stricter standards than those set in 2007 for on-road vehicles and 2010 for nonroad equipment. The legislation applies to light-duty and heavy-duty vehicles, diesel engines, and construction equipment, allowing manufacturers to implement specific exhaust fluid monitoring practices and engine management strategies outlined in recent EPA guidance documents without penalty. After the ten-year freeze expires, any new emission standards must provide manufacturers at least five years of advance notice before taking effect and must remain applicable for a minimum of three model years. The EPA retains authority to enforce prohibitions against defeat devices, approve software updates, and implement recall and warranty requirements, but must consider factors like operational disruption, equipment durability, resale value, and costs to owners and operators when developing future standards. The bill does not authorize permanent disabling of emissions control systems or exempt vehicles from otherwise applicable standards.
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