def

PACCAR Raises DEF Limp-Mode Speed to 25 MPH in Major EPA Enforcement Rollback

On July 6, 2026, PACCAR announced a software update for its MX-11 and MX-13 engines that raises the final DEF-induced limp-mode speed from 5 mph to 25 mph and extends the derate timeline from 4 hours to 160 hours. The change is part of a broader EPA effort since summer 2025 to roll back the harshest aspects of diesel emissions enforcement, responding to complaints from truckers and farmers about false alarms from failure-prone DEF sensors.