PACCAR Updates MX-11 and MX-13 Engine Software to enhance customer operations.

These changes are being made in alignment with EPA Guidance.

Denton, Texas, July 7, 2026 — PACCAR Inc. today announced that Peterbilt Motors Company and Kenworth Truck Company will implement updated software for vehicles equipped with PACCAR MX-11 and PACCAR MX-13 engines, reflecting revised U.S. Environmental Protection Agency’s (EPA) guidance on Diesel Exhaust Fluid (DEF) inducements. Trucks manufactured after July 20, 2026 will have the software installed at the factory. Trucks built after 2018 will be available for these software updates at Peterbilt and Kenworth dealerships.

In alignment with the EPA’s guidance, these updates are designed to help Peterbilt and Kenworth customers improve reliability and reduce unnecessary disruptions to their operations by:

• Having the final inducement speed limit increased from 5 mph to 25 mph
• Extending the timeline from 4 to 160 hours for component-related or fluid-quality issues before reaching final inducement speed limit
  

DEF inducements are safeguards that reduce vehicle speed and power when emissions system issues are detected. Common issues include low DEF levels or reduced Selective Catalytic Reduction (SCR) system performance. DEF inducements prompt drivers to correct the issue by refilling the DEF tank, repairing faulty sensors, or performing a system regeneration. All MX-powered vehicles remain subject to EPA emissions requirements. Vehicles requiring repairs to emissions components must be serviced to maintain compliance.

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Peterbilt Motors Company is recognized as the “Class” of the industry. With a complete lineup of diesel, natural gas and electric vehicles, Peterbilt has earned a global reputation for superior engineering, quality and craftsmanship. Peterbilt is Driving Uptime Every Day through innovative aftermarket services and advanced technology solutions delivered through its 430+ dealer locations in North America.

Visit https://www.peterbilt.com/ for more information. Peterbilt is a PACCAR Company, traded publicly on the NASDAQ as PCAR.