Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
Restore battery power to the vehicle, first of all. Put a charger on it or whatever you need to do, and let's get the electrical system up where it belongs.
If you have a theft deterrent issue, disconnecting the battery won't solve it. It would be a pretty crummy theft deterrent system if that's all it took to disable it, right? :-) So, let's get battery power back to the car, then we can do some work to see if we can get it going. What we'll do first is a theft deterrent relearn, which takes 30 minutes with the key on, so that battery needs to be charged up during this process.