Volvo Group Expands Software Update for DEF Systems

Mack Trucks and Volvo Trucks North America (VTNA), both divisions of Volvo Group, announced the implementation of new software updates for their diesel exhaust fluid (DEF) systems, making them the latest manufacturers to adopt the revised guidelines issued by the U.S. Environmental Protection Agency (EPA).

The EPA’s new provisions, published in August 2025, revise the operation of safeguard mechanisms associated with DEF systems. Among the most significant changes is an increase in the speed limit before a vehicle enters derate mode, raising it from 5 miles per hour (mph) to 25 mph. The updated rules also provide operators with more time to address issues involving sensors, components, or the DEF supply before the truck restricts its performance.

These changes are intended to provide greater operational flexibility for trucking companies and farmers by reducing the operational impact of emission-control system faults.

Volvo Group Joins Manufacturers Adopting the EPA’s New Guidelines

Volvo reported that since May of this year, its flagship models have been leaving the factory equipped with the updated software. Volvo Trucks North America’s D13 VGT and D13 TC engines now include the update in the new-generation VNL and VNR models, while Mack Trucks has implemented the same update for MP13 engines installed in the Pioneer and Anthem models.

In addition to new vehicles, the company confirmed that the updates will also be available for trucks already in service. Model year 2024 and newer trucks will be eligible to receive the updated software before the end of the summer, while vehicles built from 2014 onward will become eligible during the second quarter of 2027, Volvo Group said. For model year 2011 and newer vehicles, availability will extend through the end of that same year.

With this announcement, Volvo joins other manufacturers that have already begun implementing the EPA’s revised guidelines. Daimler Truck North America was the first to unveil its strategy, announcing in June that it had begun updating approximately 330,000 trucks equipped with Detroit DD13 and DD15 engines from model years 2021 through 2025. Newly manufactured Freightliner and Western Star vehicles already come with the updated software, while updates for trucks currently in service will continue throughout 2026.

Paccar and Cummins later announced their own update programs. Cummins stated that the new software will be available for more than 1.5 million engines used in medium- and heavy-duty trucks, including some model year 2017 engines. Meanwhile, Paccar announced that MX-11 and MX-13 engines installed in Kenworth and Peterbilt trucks will receive the new calibrations, and that all trucks built after July 20 already include the updated software from the production line.

DEF: A Key Component in Emissions Control

The changes stem from the operation of the Selective Catalytic Reduction (SCR) system, a technology used since the 2010 model year to comply with the EPA’s nitrogen oxide (NOx) emission limits. The system uses diesel exhaust fluid (DEF)—a solution consisting of 32.5% urea and 67.5% deionized water—to convert nitrogen oxides into nitrogen and water vapor before they are released into the atmosphere.

When the system detects a fault, whether due to insufficient DEF or issues with sensors and other components, vehicles activate safeguard mechanisms that progressively reduce engine speed and power, requiring the operator to correct the issue. Under the new guidelines, these safeguards will remain in place but will allow a greater operating margin before severe restrictions are imposed.

The regulatory review does not end there. The EPA has also proposed eliminating engine power derates related to DEF system faults altogether and replacing them with visual and audible warnings for the driver. If adopted, this measure would represent a significant shift in emissions compliance strategy for heavy-duty vehicles and is part of the current U.S. administration’s broader review of NOx emissions regulations.

For the trucking industry, these updates are expected to improve vehicle uptime by reducing the risk of trucks becoming nearly immobilized due to minor emissions system faults, while continuing to require the use of DEF as a critical component in controlling harmful emissions.