[gmtech1]

I believe you have a PASSKEY security system in your vehicle. Does ignition key have a chip in it? If so, and you replaced the entire column, with the lock cylinder, then the theft module is seeing the incorrect key trying to start the car. The easiest thing to do would be to take your original key to the dealer parts dept, have them cut a new key with the chip that matches your original key, but cut it to match the key from the kew column. Or you can swap the ignition lock cylinders from one column to the other.