GMC Sierra Owners Manual
To use the cigarette lighter, push it in all the way, and let go. When it is ready for use, the lighter pops back out.
Notice: Holding a cigarette lighter in while it is heating does not let the lighter back away from the heating element when it is hot.
Damage from overheating can occur to the lighter or heating element, or a fuse could be blown. Do not hold a cigarette lighter in while it is heating.