Chevrolet Cavalier Forum : “how to over-ride anti-theft so car will start?”

You'll have to contact the dealer to find out the security code or have them tell you how to disable your cars security system.

The only other way to do it would be to disconnect the battery but if you've already tried that then nothing else will work other than have the code.

I have a 00 Cavalier with the same theft system. and online solution that works is to stick the cavalier into neutral and then start the car up that way and if i remember correctly is that you cranked it once to turn on the electrical systems not trying to start the car and let it sit a good while and then try to start it up

find a shop with a TECH 2 scan tool and they can unlock the security system on the car your age newer ones are touchier then that but on the old ones its fine, if the battery gets dissconnected and the light is on on the steareo it will lock the car up and your screwed well good luck if you dont have it fixed yet

I am having the same problem with my 96 Cavalier.  Sometimes it starts, sometimes it doesn't.  Did you find out to solve the problem?