PACCAR is updating software for its MX-11 and MX-13 engines in an effort to improve vehicle uptime and minimize unnecessary operational interruptions tied to emissions system events.
The software changes, which affect Kenworth and Peterbilt vehicles equipped with PACCAR MX engines, are being introduced in response to revised guidance from the US Environmental Protection Agency (EPA).
Trucks manufactured after July 20, 2026, will receive the updated software at the factory, while eligible vehicles built after 2018 will be able to receive the update through Kenworth and Peterbilt dealerships.
According to PACCAR, the update modifies how Diesel Exhaust Fluid (DEF) inducements are handled. DEF inducements are safeguards that reduce vehicle speed and power when the emissions system detects certain issues. These events can be triggered by conditions such as low DEF levels, fluid-quality concerns, or reduced Selective Catalytic Reduction (SCR) system performance.
Under the updated software, the final inducement speed limit will increase from five mph to 25 mph. The company is also extending the timeline before a vehicle reaches the final inducement stage for component-related or fluid-quality issues, increasing that period from four hours to 160 hours.
PACCAR says the revised parameters are intended to provide fleets and owner-operators with additional time to address emissions-related issues while helping reduce disruptions to vehicle operations. Drivers will still be required to correct underlying problems by refilling DEF tanks, addressing faulty components, or completing required regeneration procedures.
The company emphasized that the software changes do not alter federal emissions requirements. Vehicles experiencing emissions system faults that require repairs must still be serviced to maintain compliance with EPA regulations.
For service providers and fleet maintenance operations, the update may help reduce situations where vehicles are forced into severe speed restrictions before operators have a reasonable opportunity to diagnose and resolve an issue. The extended inducement timeline could be particularly beneficial for trucks operating in remote locations or on routes where immediate service access is limited.
The software update will be available through Kenworth and Peterbilt dealer networks for qualifying MX-powered vehicles already in operation.
PACCAR is a global technology company that designs, manufactures, and supports premium commercial vehicles under the Kenworth, Peterbilt, and DAF brands. The company also provides powertrain solutions, financial services, and information technology products for the transportation industry. For more on the company, visit www.paccar.com.