i will try and be as precise as i can in explaining this problem, please bear with me. i have a 2006 silverado 2500hd. love it. had it for the last 10 years. no major problems. about 6 months ago it was stolen, they used a screwdriver to jam the ignition lock and took it. i found it on the street, got it back, i replaced the the ignition lock cylinder, added an alarm system and kill switch. has worked flawlessly as my daily work truck.
last night i get home, park in the driveway, go to shut it off and the key turns JUST far enough to shut the engine off, but not far enough to shut down the dash lights. tried starting it a couple more times, shifting it to make sure it was fully in park, tried it in the driveway, out in the street where its flat, nothing, the key does not turn enough to fully shut off the truck. engine does shut down, but dashboard lights and radio stayed on. after a little jiggleing, the key did come out but the lights remained on. i can grip the plastic housing around the keyhole and start the truck without the key.
went to autozone and got another new ignition lock cylinder, same exact thing. the new lock cylinder turns the truck on just fine, it drives and feels as it always has, but when you go to shut the truck off, the engine will shut down but some dash lights stay on and the key will not physically turn enough to feel like its in the off position. the key is a little hard to take out, but not to where it feels stuck. i took the ignition switch out and it looks and feels just fine. but, and this is where in hitting a wall, the gear/cog, in the ignition switch matches to a gear/cog up in the steering column. it seems as if that little gear (after looking for a while i guess its called an "Ignition Switch Actuator Sector") should turn more to allow the key to turn fully off. has anyone ever heard of that breaking or something getting into that area and jamming it?
im fairly mechanical and this does not feel like an electrical issue, but more of something physically stopping it from turning off. it seems to hit a solid wall. no change if the battery is hooked up or disconnected.
my next attempt is going to be to remove the steering wheel and the ignition lock housing and see if anything broke or is stuck in there.

any thoughts, ideas or advice is appreciated.

 

It sounds like the ignition starter switch has gone defective on you. It is a common problem in GM vehicles that use this particular kind of ignition stater switch (also known as ignition switch). I carry one as a spare in my 2004 TrailBlazer which uses the same switch. The question with these switches not if the switch will go bad, but rather when will the switch go bad.

My recommendation is to replace it using a switch from Standard Motor Products (non T series), BWD (non P series), or NAPA Echlin. I would shy away from Dorman, DuraLast, and Carquest switches due to manufacturer concerns.

Good Luck!