key wont turn

Try moving the steeing wheel while trying to turn the key. If that doesnt work the part the key goes is needs to be taken out and rebuilt or replaced

Chevy and other gm makes have what is called a sidebar in the ignition cylinder. Over time it gets locked in place. This is the only explanation for the correct key spontaneously not working anymore. It can be forced to turn with vice grip after the plastic is peeled away to get a grip. The key must also be inserted to align the wafers, then you can force it with the vice grip. Once turned you can remove it (get instruction on YouTube) and then refurbish the sidebar (shave it down smaller) with a dremmel tool or hand-file. The refurbished cylinder can now last you another 180,000 miles haha good luck.

Had this problem with my neighbor's Tahoe yesterday. Looked like the classic "wheels turned" problem, but nothing worked. I stared at the dashboard for a minute and noticed there was no release for the parking brake so it must be tied into the computer. I tapped the parking brake and, Voila (pronounce the "V") the key turned!

Insert the red nozzle extension on the aerosol oil can lined up with were the pin is (right by the upper thumb part), squirt the oil, and gently tap the outside of the tumbler. Worked perfectly for me after I tried everything else. Operates perfectly now. Good luck!!!!!!