Made 3 keys and it wouldn't start" the theft deterrent flashes on?

I suspect when you programmed the keys you used the method attached below which requires two previously programmed keys.

If that is the case, then we are not going to be able to use this method after you replaced the PCM.

Unfortunately, we are going to have to use a scan tool in order to program these keys.

I am attaching this process as well below.

Please run through this info and let me know what you find.

Thanks