(CVBN: Chico, CA) — North America’s leading Class 8 truck OEMs and heavy-duty engine manufacturers have aligned behind a sweeping, industry-wide software overhaul that effectively eliminates the dreaded 5-mph “limp mode” caused by Selective Catalytic Reduction (SCR) and Diesel Exhaust Fluid (DEF) sensor faults.
Following revised guidance from the Environmental Protection Agency (EPA) earlier this year, heavy-duty engine builders—including Daimler Truck North America, Cummins, PACCAR, and Volvo Group—have initiated software rollouts across new production lines and millions of in-service commercial vehicles.
Key Operational Changes
- Floor Speed Raised: Final inducement speed restrictions increase from 5 mph to 25 mph, giving drivers the power and control needed to navigate off high-speed highways, pull off steep grades, and reach service facilities safely.
- Extended Grace Windows: The countdown before reaching final derate expands from as little as 4 hours up to 160 operating hours (or roughly 8,400 miles), giving fleets time to complete active dispatches before scheduling repairs.
- Streamlined Deployment: Because the EPA cleared these specific engine ECM calibrations, manufacturers are deploying updates via Over-The-Air (OTA) downloads and routine dealer service visits without requiring standard emissions recertification hurdles.
OEM Deployment Breakdown
| Heavy-Duty OEM / Engine Maker | Fleet & Platform Scope | Delivery Method |
| Cummins | 1.5M+ engines (MY2017+ on-highway SCR platforms) | Distributor & OEM networks |
| Daimler Truck North America | ~330,000 Freightliner/Western Star trucks (Detroit DD13/DD15) | Factory standard + Dealer retrofits |
| PACCAR (Kenworth & Peterbilt) | MY2018+ models powered by PACCAR MX-11 and MX-13 engines | Factory standard + Dealer retrofits |
| Volvo Group (Volvo & Mack) | Phased rollout covering post-2010 models (VNL/VNR & Anthem/Pioneer) | Factory standard + OTA + Dealer retrofits |
The Operational Bottom Line
By replacing aggressive derates with manageable grace periods, the commercial freight sector is mitigating one of its most expensive uptime hazards. While emissions compliance remains fully mandatory and active fault codes still require resolution, false sensor triggers and minor aftertreatment issues will no longer force 80,000-lb line-haul tractors onto dangerous highway shoulders.
