Suggest starting at the basics; fuel, spark. Check the fuel pressure and check for spark when cranking.
As far as the Security lite - I do not think the factory system has a starter interrupt relay. It will only sound the horn if a door is opened without using the key to unlock.

Keep after it....sounds like this could be a good puzzle.

 

Just a quick little update. I have put in a brand new ignition switch and have tried to do passlock relearn but after 20 minutes the security light is still staying on. Guess Im going to have to take it in to get it manually cleared? Lights that are lit on dash; SES ABS Security Airbag. Air bag because I havent put back in dash yet and havent replaced fuse. As far as the others I have no clue why they are now on. Someone please help!

Ok, so, I actually got it to run for a second. Will the passlock keep it from letting fuel through? I can put starter fluid in and it will run until its gone. Im getting somewhere. The beast started for about 3 seconds then stopped. Meaning for some reason it is not getting fuel. Passlock is still on... Will this keep injectors from working?

Now for a major question. Since I can't get the passlock relearn after putting in another new ignition switch, it says "if this method does not work after replacing the ignition switch, then the system will have to be force relearned using a Tech2 or comparable full feature scan tool".. My plug apparently won't read. What can I do now? I know that there is a lot to take in but like i said before, you guys are great and have a lot more experience with these vehicles than I do. Any help is welcomed. Thanks

 

There are a VERY limited number of scan tools outside the GM Tech2 tool that can do a forced relearn, but you will definitely need to get the DLC working first. Check the CIG fuse (or check for power at the cigarette lighter); it powers the DLC port.

If passlock is what is interfering with things, then you should be able to put the key in the 'run' position for 10-15 minutes, then turn it immediately to the start position and the engine should start & run.

 

So even though I can't get an actual passlock relearn, it will still start if I keep the key in the on position til the security light goes off? I waited 20 minutes and the light was still on.. I checked fuses and everything. Everything looks good. I'm just wondering now if there could be more than one problem going on? If the I can't get data from the data line and the fuses are ok... Where do I go from there? That's originally why I thought the PCM. Any thoughts?