A primary fuel economy improvement derived from current electronic engine controls for heavy duty line haul trucks is their road speed limiting feature. PT PACER cost-effectively integrates this primary benefit with the well-established Cummins hydromechanical PT fuel system. The product, developed by Cummins Engine Company, Inc., and its subsidiary Cummins Electronics Company, Inc., was introduced recently to the market after a one-year development and launch period. This product is tightly integrated with the fuel system and engine, resulting in stable and smooth control, tamper resistance and reliability. Onboard diagnostics, which were designed to detect system failures, enhance troubleshooting capability and tamper resistance. Extensive component design validation testing and environmental testing along with laboratory and vehicle system testing were conducted prior to field test. Field test experience has provided confidence that this new system is an effective, reliable product delivering the intended benefits to the customer.