Cummins and PACCAR are updating diesel engine software to give truck operators more time to address certain diesel exhaust fluid system issues before vehicles reach the most restrictive operating limits. The updates follow revised U.S. Environmental Protection Agency guidance on DEF inducements, which are safeguards that reduce vehicle speed and power when emissions system problems are detected. The changes do not remove emissions compliance requirements, and vehicles with emissions component issues must still be repaired. Cummins is updating certain engine calibrations to provide operators with more time to complete needed repairs and help reduce unnecessary downtime related to DEF inducements. The revised calibrations increase the time before certain DEF-related inducements occur and increase final inducement speeds in some circumstances. The updates extend the time to initial and later derate events for certain tampering and DEF quality conditions, while also increasing the final derate speed from 5 mph to 25 mph. According to Cummins, the updates are intended to provide additional operating flexibility while maintaining emissions system requirements. Cummins has begun offering revised calibrations for more than 1.5 million engines in medium- and heavy-duty trucks, including certain truck applications dating back to model year 2017 and certain motorcoach applications dating back to model year 2018. Timing will vary by engine platform and model year. Customers can contact a local Cummins distributor or dealer to schedule available updates. PACCAR also announced updated software for vehicles equipped with PACCAR MX-11 and MX-13 engines. Trucks manufactured after July 20, 2026, will have the software installed at the factory, and trucks built after 2018 will be eligible for the updates at Peterbilt and Kenworth dealerships. These changes will increase the final inducement speed limit from 5 mph to 25 mph and extend the timeline from four hours to 160 hours for component-related or fluid-quality issues