2012 GMC Sierra Owner's Manual - Page 305

Driving and Operating 9-29 Fast Idle System If the vehicle has this feature it is available only with cruise control. The manual fast idle switch is operated using the cruise control buttons located on the left hand side of the steering wheel. This system can be used to increase engine idle speed whenever the following conditions are met: ... When the fast idle is active the Driver Information Center (DIC) will display "FAST IDLE ON." One of the following actions will turn off the fast idle: . . Retained Accessory Power (RAP) The following vehicle accessories can be used for up to 10 minutes after the engine is turned off: ... Pressing the brake. Selecting the Cruise Control Cancel button. Releasing the Parking Brake. The transmission shift lever is moved out of P (Park) or N (Neutral). Selecting the Cruise Control On/Off button when it was previously on. Pressing the Cruise Control Set switch a second time. Pressing the accelerator greater than a quarter of the way down. Turning the ignition switch to the LOCK/OFF position. Audio System Power Windows OnStar System (if equipped) Sunroof (if equipped) . . The park brake is set. The brake pedal is not pressed. The vehicle must not be moving and the accelerator must not be pressed. To enable the Fast Idle System, press and release the Cruise Control On/Off button and ensure that the switch LED is lit. Press and release the Cruise Control Set switch. Engine speed will be held at approximately 1200 RPM. . . To control the fast idle: . . 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. . .