I have a 2000 Silverado with over 300,000 miles and to today when I tried to crank it the ignition switch would not turn at all. I tried turning the steering wheel to unlock it but it will not turn. When I put the key in the ignition the buzzer sounds but that it. I've been having that problems with it within the last month but I would turn it a few times and it would unlock and start. Could this be a bad key or the switch itself.

 

Probably wear on both of them!!

 

Thanks for the info. The cylinder was bad. By luck I got the old one out. I had to stick a zip tie between the cylinder and the housing to push the little latch down so I could get the cylinder to turn. Then I could push the little latch on the end down and the cylinder came out. I bought a new on for about $54.