New software for DEF derate updates for eligible PACCAR and Cummins engines built between 2019 and 2026 are giving operators significantly more time to reach a repair facility when a diesel exhaust fluid (DEF) related issue comes up. Cummins has begun rolling out updated engine calibrations, following revised guidance from the U.S. Environmental Protection Agency (EPA), that extend the window before a DEF inducement forces a truck to slow down, while also raising the final derate speed so a truck can remain more mobile in traffic on the way to a repair facility.
For fleets and owner-operators, the change means more time to respond to a DEF-related issue, more flexibility to complete a load or trip, and more time to reach a repair facility before the final derate.
What’s Changed on DEF Derate Updates?
| DEF Inducement Stage | Previous | Updated |
|---|---|---|
| Time before final DEF-related derate | 4 hours | 160 hours |
| Final derate speed | 5 MPH | 25 MPH |
These updated calibrations apply to eligible PACCAR and Cummins engines from model years 2019 through 2026, and timing varies by engine platform and model year. For heavy-duty truck and tractor engines specifically, the updates extend the time to initial and subsequent derate events for certain tampering and DEF quality conditions, in addition to raising the final derate speed. Eligible motorcoach applications also gained added flexibility, including more time before initial inducement and removal of a secondary derate step in certain conditions.
Why the DEF Derate Update Matters
Selective catalytic reduction (SCR) systems rely on DEF to keep modern diesel engines within emissions requirements, and DEF-related inducements exist to make sure operators keep tanks filled and systems in good working order. Emissions compliance remains mandatory under the updated calibrations. What has changed is the amount of runway operators get before a DEF issue forces a slowdown.
“We appreciate EPA’s engagement with industry stakeholders and view the revised guidance as an important step toward addressing customer concerns in a practical, compliance-focused way,” said Brett Merritt, vice president and president of Cummins’ Engine Business, in a statement announcing the update. “Cummins has acted to support reliable implementation of these updates, help customers and operators reduce unnecessary downtime, and continue to meet emissions requirements.”
Cummins says the rollout covers more than 1.5 million medium- and heavy-duty truck engines, with certain applications dating back to model year 2017 and motorcoach applications dating back to model year 2018. Eligibility and applicable model years vary by engine platform and application.
Sources
- U.S. Environmental Protection Agency: https://www.epa.gov
- Cummins Inc., “Cummins Supports Customers with Updated DEF Inducement Calibrations,” Business Wire: https://www.businesswire.com/news/home/20260706893883/en/
Get Your Truck Updated
Want to know if your truck qualifies for DEF derate updates? Contact GreatWest Kenworth. Our service team can check your engine’s eligibility for the updated calibration and help schedule the required software update.
Call GreatWest Kenworth at +1 (888) 253-7555 or visit greatwestkenworth.com to schedule service.
