Windows - GMC 2010 T-Series Owner's Manual

When the doors are locked, they can't be opened using
the inside handles until the manual lock is pulled out.

Windows

WARNING:
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.
2-4
Manual Windows
Turn the hand crank on each door to raise or lower the
window.