Need pass key decoder module part number 16150920

you dont copy down vin and have dealer cut a key using vin number

First off Henry ,what kind of problem are you having ? A bad ignition switch can cause a no start problem , could lose power to some other systems on the vehicle , turn signals , radio , heater . It depends what all is powered up through the switch ! Would need to look at a wiring diagram ! Powers the pass-key decoder module - for anti-theft !

If you have the visible chip on the key.(that is actually a resistor) take the key to radio shack and have them measure the resistance of the key. Then buy from radio shack a resistor of the same resustance. Then under the dash coming from the column cut the small yellow wire and the black wire. Now splice your new resistor to the black and yellow wire. Your car should start. I have a video on youtube and there are plenty of others on there also.

The ecm fuse also powers the pass-key module on the key barrel.
See diagrams below. I recommend you probe the starter enable relay socket to see if it is getting the ground signal from the pass-key decoder whole someone tries to start the car.

your vehicle is equipped with Personal Automotive Security System (PASS-Key II(R)).
This security system is designed to prevent vehicle theft by disabling fuel system and starter unless an ignition key with a specific electrical resistance is used in the ignition key lock cylinder. PASS-Key II(R) system operates using sensing contacts, which are located in the ignition key lock cylinder. These contact a resistor pellet located in the ignition key. When lock is rotated, battery voltage is applied through appropriate fuse and resistor pellet to theft deterrent module (except Century), or body control module (Century). Pellet resistance is then compared with programmed value in the theft deterrent module or Body Control Module (BCM).
System components include ignition key, ignition key lock cylinder, theft deterrent module (except Century) or BCM (Century), theft deterrent relay and Powertrain Control Module (PCM). The PASS-Key II(R) system can also be supplied as a special equipment option on some vehicles

It will reset itself after about 10 minutes. You just have to wait until you hear a click and the pass key light goes off.
Be sure to clean the little metal strip on your key while you're waiting...

When the ignition switch is turned on, the immobilizer control module sends a challenge signal through the antenna around the ignition switch to the transponder chip in the ignition key. The transponder key responds with an encrypted key code. The immobilizer module then decodes the key code and compares it to the list of registered keys. When the engine is started, the ECM sends a request to the immobilizer module over the data bus to verify the key is correct. If an attempt is made to start the vehicle with an invalid ignition key, the immobilizer module sends a message over the data bus to the instrument cluster to flash the anti-theft indicator lamp. If the ECM does not receive a "valid key" message from the immobilizer module within 2 seconds of engine start up, the ECM will disable the fuel injectors to kill the engine. You'll need to get a new key and get it registered in the immobilizer control module. You'll need a scan tool, the VIN number, the date manufactured and a factory-assigned PIN number.

The fuse marked "Crank" is usually a 10 amp fuse used for the starter enable relay circuit and the pass-key decoder module, and the starter motor should not function without that fuse unless the circuit has been by-passed. If the vehicle has a pass-key decoder module then that fuse can prevent the vehicle from starting and running.

The dealership can bypass the security chip no problem. The chip is a resistor and they use a resistor of the same value at the bottom of the steering column to bypass. resistors and soldering are required.

bolted to the vent box behind the center console , also check the VATS fuse in the convenience center.