2009 GMC Yukon Owner's Manual - Page 135

Active Fuel Management™ Vehicles with V8 engines may have Active Fuel Management™. This system allows the engine to operate on either all or half of its cylinders, depending on the driving conditions. When less power is required, such as cruising at a constant vehicle speed, the system will operate in the half cylinder mode, allowing the vehicle to achieve better fuel economy. When greater power demands are required, such as accelerating from a stop, passing, or merging onto a freeway, the system will maintain full-cylinder operation. If your vehicle has an Active Fuel Management™ indicator, see DIC Operation and Displays (With DIC Buttons) on page 3-52 or DIC Operation and Displays (Without DIC Buttons) on page 3-57 for more information on using this display. Automatic Transmission Operation If the vehicle is a Two-mode Hybrid, see the Two-mode Hybrid manual for more information. If the vehicle is has an automatic transmission, it has an electronic shift position indicator within the instrument panel cluster. This display comes on when the ignition key is turned to the ON/RUN position. There are several different positions for the shift lever. Hydra-Matic® 4-Speed Automatic Transmission 2-29