2000 Monte Carlo won't start.
 

Hi, I just bought my 2000 Monte Carlo not even 6 months ago. Its been sitting for almost 4 months. I've had to replace my entire back end because my railing bars were bent. Now my car won't start. My security system went off so I had it towed to the dealership and had the pass lock sensor reset but it still won't start. The shop manager at the dealership said my car wasn't interacting with the ECM when I put the key in the ignition it turns and all the dash lights come on radio etc. But my fuel gauge says low fuel which I know isn't true because I have a half a tank of gas. And my security light is still on. When I try to start it so!etimes I'll get a click click click but now I'm not getting nothing at all. Dealership said it might be a wiring problem or a bad ECM is there anyone out there that knows what is going on with my car please help me!!!!!!!!?
If it helps my battery was dead when I was getting the click click click noise I've since charged the battery over night. Now I don't get anything when I turn the key to start only my lights go out and come back on wen I release the key it doesn't even make an attempt to start. SOMEONE PLEASE HELP ME!

Check all the grounds.

Fuel gauge information comes from the PCM (powertrain control module). It also controls the starter. Sounds like it's bad.