The US Environmental Protection Agency (EPA) is relaxing its regulations on diesel exhaust fluid levels, aiming to reduce sudden speed and power losses. Administrator Lee Zeldin announced this move at the Iowa State Fair, stating that the current system is “unacceptable” for small businesses.
Most modern diesel engines rely on diesel exhaust fluid (DEF) to reduce nitrogen oxide emissions by 99%. However, some drivers have removed their trucks’ emissions equipment due to performance concerns. To address these issues, new EPA requirements taking effect in model-year 2027 will no longer force sudden power loss after running out of DEF.
Instead, the EPA will issue guidance for manufacturers to update software, allowing drivers and equipment operators to continue using their vehicles with reduced performance until they refill the fluid. The goal is to make the engine derating process more gradual, reducing the need for drivers to slow down significantly when low DEF levels are reached.
The updated rules apply to both new and used diesel trucks. Heavy-duty semis will be limited to 25 mph after four work weeks of reduced performance, while heavy-duty pickups will only be limited to 45 mph after 4,200 miles or 80 hours with low DEF levels.
Source: https://www.thedrive.com/news/epa-tells-truck-makers-to-stop-forcing-limp-mode-for-low-def