A Packer MX-13 engine. The parent company of Kenworth and Peterbilt will introduce updated software for vehicles equipped with MX-11 and MX-13 engines. (Packer Inc.)
key takeaways:
- The EPA guidance increases the final spur speed by 5 mph to 25 mph and extends the timeline for addressing emissions system issues.
- Cummins plans updates for more than 1.5 million engines across multiple model years, the rollout of which will vary by platform and application.
- Packer and Daimler Trucks North America are implementing similar updates to new and in-service vehicles through 2026.
Packer and Cummins have begun rolling out software updates that include revised diesel exhaust fluid induction parameters, allowing trucks to increase the minimum speed before refilling DEF tanks or repairing sensors.
The updates follow revised guidance from the Environmental Protection Agency in August 2025. EPA issued guidance to provide carriers and farmers more flexibility and uptime.
Selective catalytic reduction (SCR) technology uses DEF to convert nitrogen oxides into nitrogen and water, supporting compliance with EPA emissions standards.
There are built-in safeguards on induction trucks and tractors that ensure that the emissions system works properly by cutting down on vehicle speed and power should problems be detected.
5 mph to 25 mph
Under the revised guidance, the speed limit at the final spur will be increased from 5 mph to 25 mph, and the time to reach the final spur for component-related issues will be extended.
Cummins is offering updates for more than 1.5 million engines in medium and heavy duty trucks, including some model year 2017 trucks, the company said July 6.
Columbus, Ind.-based Cummins has begun offering the update on some model-year 2026 production engines, with implementation timing varying by engine platform and model year. A spokesperson told Transport Topics on July 7 that additional model-year 2026 on-highway engines are expected to incorporate the calibration changes into production starting in mid-August.
For off-highway applications, updated calibrations are planned for model year 2027 engines and newer, he said.
The spokesperson said the updates are available for all EPA-certified on-highway engines that use SCR technology, while for off-highway applications, the changes apply to EPA-certified engines as well as EPA/EU engines that use SCR technology.
“We appreciate EPA’s partnership with industry stakeholders and view the revised guidance as an important step toward addressing customer concerns in a practical, compliance-focused manner,” Brett Merritt, president of the engine business, said in a statement. “Cummins has worked to support the reliable implementation of these updates, helping customers and operators minimize unnecessary downtime and meet emissions requirements.”
MX-11, MX-13 engines
Packer, the parent company of Kenworth and Peterbilt, will introduce updated software for vehicles equipped with MX-11 and MX-13 engines, the company said July 6.
The parent company said the software will be installed at the factory on trucks manufactured after July 20. Trucks manufactured after 2018 can receive the update at Peterbilt and Kenworth dealerships.
Packer and Cummins followed Daimler Trucks North America in issuing software updates.
DTNA said on June 22 that it began rolling out the update in February to approximately 330,000 in-service vehicles with DD15 engines (model years 2021-2025) and DD13 engines (model years 2022-2025).
Updates to the Freightliner and Western Star trucks will continue throughout 2026.
Freightliner and Western Star vehicles equipped with Detroit engines are already shipping with the updated software.
What is def?
The SCR technology and hence the DEF requirement was introduced to meet the 2010 model-year EPA mandate. DEF is a non-toxic, colorless and odorless solution consisting of 32.5% urea and 67.5% deionized water.
Industrial urea manufacturing involves the chemical reaction of ammonia and carbon dioxide, with the most cost-effective method using natural gas as a feedstock.
Engines will still need DEF. The deceleration prompts the driver to correct the problem, usually refilling the DEF tank, repairing a faulty sensor or component, or performing a regeneration cycle.
But in March, the EPA approved a guidance update that allows truck makers to replace the urea-quality sensor with a nitrogen oxide sensor.
