For years, truck drivers and farmers have complained about newer diesel engines that require DEF systems. In addition to sudden shutdowns, drivers have reported reduced engine lifespan and performance.

Last August, the EPA announced new guidance for engine and truck manufacturers. The agency urged them to update the DEF system software on current vehicles.to prevent sudden shutdowns.

That guidance applies only to model year 2026 and older trucks. DEF systems for model year 2027 and newer trucks are regulated under a separate heavy-duty NOx rule passed in 2022.

EPA is demanding that info from the top 14 manufacturers that account for more than 80% of all products used in DEF systems. Manufacturers have 30 days to comply.

What does the EPA plan on doing with information? Simply put, the agency is setting the stage to withdraw the 2022 heavy-duty engine and vehicle NOx rule. While that may not get rid of DEF, it could eliminate derating requirements “permanently” and “entirely,” EPA Administrator Lee Zeldin said.

https://landline.media/epa-doubles-down-on-def-overhaul-demands-data-from-manufacturers/