2010 GMC Sierra 1500 Crew Cab Owner's Manual - Page 163

B (ACC/ACCESSORY): This position lets things like the radio and the windshield wipers operate while the engine is off. Use this position if the vehicle must be pushed or towed. C (ON/RUN): This position can be used to operate the electrical accessories and to display some instrument panel cluster warning and indicator lights. The switch stays in this position when the engine is running. The transmission is also unlocked in this position on automatic transmission vehicles. If you leave the key in the ACC/ACCESSORY or ON/RUN position with the engine off, the battery could be drained. You may not be able to start the vehicle if the battery is allowed to drain for an extended period of time. D (START): This is the position that starts the engine. When the engine starts, release the key. The ignition switch returns to ON/RUN for driving. A warning tone will sound when the driver door is opened, the ignition is in ACC/ACCESSORY or LOCK/OFF and the key is in the ignition. Retained Accessory Power (RAP) The following vehicle accessories can be used for up to 10 minutes after the engine is turned off: ... Audio System Power Windows OnStar® System (if equipped) Sunroof (if equipped) These features work when the key is in ON/RUN or ACC/ACCESSORY. Once the key is turned from ON/ RUN to LOCK/OFF, the windows and sunroof continue to work up to 10 minutes until any door is opened. The radio continues to work for up to 10 minutes or until the driver door is opened. 3-25