Mack and Volvo Expand DEF Software Updates to Cut Derate Downtime

Mack Trucks and Volvo Trucks North America are expanding diesel exhaust fluid inducement software updates across new and in-service commercial vehicles. The changes follow updated EPA guidance intended to give operators more time to correct certain emissions-system faults before a truck reaches its most restrictive reduced-speed condition. A DEF inducement, often called a derate, lowers power or speed when the selective catalytic reduction system detects a problem.

Under the updated approach described by Heavy Duty Trucking, the final inducement speed increases from 5 mph to 25 mph and the available repair window can expand from four hours to as much as 160 hours. That extra time may help a driver reach qualified service and reduce the risk of a truck becoming effectively immobilized far from a repair facility. It does not make a warning safe to ignore or remove the need to correct the underlying fault.

Mack and Volvo began installing the software on selected new models in May. Both manufacturers plan remote availability for eligible model-year 2024 and newer trucks by the end of summer 2026, broader post-2014 coverage by the second quarter of 2027, and dealer availability for eligible post-2010 vehicles by the end of 2027.

Fleets should verify eligibility by VIN, engine configuration and manufacturer instructions before scheduling an update. Drivers should continue reporting DEF warnings immediately and follow company procedures. The expanded repair window is an uptime safeguard, not permission to operate indefinitely with an active emissions-system defect.