GMC Sierra Owners Manual
WindowsKeys, Doors, and Windows / Windows
Leaving children, helpless adults, or pets in a vehicle with the windows closed is dangerous.
They can be overcome by the extreme heat and suffer permanent injuries or even death from heat stroke. Never leave a child, a helpless adult, or a pet alone in a vehicle, especially with the windows closed in warm or hot weather.
The vehicle aerodynamics are designed to improve fuel economy performance. This may result in a pulsing sound when either rear window is down and the front windows are up. To reduce the sound, open either a front window or the sunroof (if equipped).