My ignition will not turn with key on my 2004 avalanche

Check the ignition switch at the base of the steering column - it may have come loose or needs replacing.

Is the ignition key going all the way to off, if it isn't then the key cylinder or the lock assembly may be the problem.

I, feel sorry for you, after reading your problem, but don't worry you visit the Reliable-Store they will help you for sure.
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Change ignition barel with keys

Turn the wheel a little bit in either direction while you turn they key. Steering lock clicks into place when key is out.---------------------------------------------------------------------
Diagnostic VAG

The Avalanche are famous for the dead battery of not driving for 30 days, Your ECM and various module has a parastatic draw that is normal for you vehicle.You also have the ignition problem. Even though you turn off the ignition remove the key the ignition draw power and this has been a porblem with your year make and model You will need to replace the ignition switch Here is the TSB Bulletin No.04-06-03-002.

I would suggest checking/replacing coil packs, and fuel pump operation. If they are good maybe a bad ignition switch is possible.

You avalanche may be in security mode. If this is the case, you will have to call the dealership and get the code. If that is not the case, you have a bad ignition. You will have to change your ignition box and lock cylinder. Make sure your shifter is all the way up, just in case the cable broke.

Turn on the ignition with engine OFF.
Try to start engine, then release the key to ON
Wait 10 or more minutes till SECURITY TELLTALE turns OFF.
Turn OFF the ignition, wait 5 seconds.
Repeat this procedure 3 more times, it takes 30 minutes.
You must turn the ignition key OFF before starting the engine.
To be on the safe side OFF means take the key off, and hold on your hand for 5 seconds.
If you missed something visit GM dealer, and they gladly will provide you a print out of this procedure.

Buy a Haynes manual for the vehicle ( most auto stores carry them). With this manual you can do nearly any repair on the vehicle, they give you step by step directions.