Key will not turn

Sounds like the ignition switch may be broken internally if it is not locking the wheel or the shift cable needs replacement. Here are instructions for both.

The ignition switch contains the wiring and electrical switching portion of the column mounted ignition assembly. The ignition switch includes wiring pigtails which connect it to the base of column connector, the Passlock Sensor on the ignition lock cylinder case, and other components. The wiring for the Passlock Sensor is unaffected by ignition switch position. The electrical switch portion is operated by the key and lock cylinder when they are rotated within the ignition lock cylinder case. The ignition switch operates the crank relay regardless of the status of the Passlock System.

Check the diagram below of the ignition switch and get back to us.

You have to see if it is in the shifter or ignition, you could take the center console apart and disconnect the shifter and see if it moves freely, if it does then it is in the ignition. Before you do this check the BTSI fuse in the under hood fuse block see if it is blown. I have had a lot of problems with the ignition cylinders on these, if it is the lock cylinder sometimes they have to be drilled out.(Will worry about that if it is the problem) these are the only suggestions I can give for now, post back with what you find and will advise on the next step.

By disconnecting the shifter you kind of ruled out that it is in the shifter and probably in the ignition. To make sure you could disconnect the ignition. If you do replace the ignition the theft deterrent needs to be relearned, which I will explain after you find out what is wrong. Post back with any other questions.

The steering on all the new or newer cars do not lock it is normal. As far as it being computer controlled and preventing it from turning has nothing to do with it, the ignition is mechanical, I would not drill it out still bolted to the dash, remove the ignition disconnect the connectors. If you take the dash bezel off around the IPC and then take the IPC out you can unbolt and access the ignition.(Much easier but a little more work) You do not want to destroy the ignition too much because there is the pass-lock chip in the housing. You might want to get a price from the dealer on an ignition lock case and switch. They will code it to the key and put the housing together which makes it easier. Post back if you get stuck.

If you step on brake pedal, does shifter move to all positions?

If so, then ignition lock cylinder or key itself.

You can call a locksmith to repair ignition cylinder onsite.

Only advise I can give is, Insert the key to the ignition lock cylinder.
Remove the ignition lock cylinder from the switch:
4.1. Using a small curved tool or an L-shaped hex wrench, depress and hold the detent on the ignition lock cylinder. If you cannot locate the detent with the tool, remove the radio. View the detent through the radio opening. Refer to Radio Replacement in Entertainment.

4.2. Turn the key to the ON/RUN position.

4.3. Pull the ignition lock cylinder out with the key.

Remove the key from the lock cylinder.
If this does not work, you have to cut or drill the ignition cylinder out. I have done a lot this way because they never want to come out. Post back with what you find.

Good news!

You may want to get a new key made, especially if the old one has any rough edges.

What do you mean? Where did you get it from parts store or dealer? Are you replacing just the ignition lock or the lock cylinder? If you bought it from the dealer they usually put it together and code it for you, then you can just put it back together and relearn the pass-lock system. I need a little more detail to what exactly you are doing.

There are four things that I see over and over again, that keep an ignition lock cylinder from turning.

1.
The steering wheel lock is under pressure.

When you turn off your car and remove your key.
A spring loaded post sticks up in to one of many holes in the steering wheel.
This locks the steering wheel in place, making your car harder to steal, because a bad guy cant turn the steering wheel if they somehow get your car started without the key.

But this can also keep you from turning the ignition lock.
If the steering wheel is under pressure because your front wheels are against a curb, or you have the wheel cranked all the way to one side or the other. The pressure from the steering wheel on the spring loaded post keeps you from being able to turn the key.

So while trying to pull the steering wheel one direction or the other, try to turn the key, this may solve your problem.

2-A.
The pins are not falling into place.

You kinda need to know how a lock works for this part.
Look at a key and you will see there are different depth cuts in it.
Those different cuts correspond with different length pins in the lock cylinder.
See how the red pins are of different length?
But with the key inserted, they are all even with the blue pins.

When the red pins are held in the correct position by the correct key, the spring loaded blue pins are flush with the outer housing of the lock, and the red pins are flush with the inner cylinder of the lock
And thus the inner cylinder can be rotated.

If debris such as pocket lint, ear wax, or just plain old dirt gets into the pins and causes enough friction for the spring loaded blue pins to not be able to push the red pins back in place.
Then the red pins will be partially stuck in the hole for the blue pins and the cylinder can not turn.

Putting the key in the lock and then tapping on it with a small hammer may help until you have the chance to have the lock cleaned.

Do a search for the word "bump key" if you want to know more about how a lock cylinder works.

2-B.
The same goes for if a key is worn out.
If a key is badly worn, then it will not put the red pins in the correct spot and some of the pins will keep the cylinder from turning.

If your key is worn out, try a spare if you have one.
Or put the key in and "Jiggle" it while trying to turn the lock.

3.
A problem with the interlock cable from the gear selector to the lock cylinder. Make sure you are completely in park.
You pretty much have to take things apart and visually inspect it to verify this problem.

4.
A mechanical problem with the linkage from the lock cylinder to the electrical part of the ignition switch.

good luck

This is not good. That means that the there might be a scratch on the inside of the ignition housing. You could try taking it back out and apart and lubing it. This is hard to answer without being there to see what is happening. You might want to take it back to AutoZone and get one from GM, they usually put them together and make sure they work.