2003 Monte Carlo SS NOT STARTING!!!

After coming back from a week long conversation, I get back to my car to find it doesn't unlock with the remote. I proceed to manually unlock my car and much to my dismay, when I got to start the car, the lights were dim, radio didn't work, and of course the car did not start. Thought it was just the battery, so I jumped it. The lights all worked fine, but the radio still did not come on and the car didn't even crank, let alone start. I'm pretty sure I heard the fuel pump kick on. I've replaced the battery and that didn't work either. So the battery cables are securely connected, they are not corroded. I had it towed to an auto shop and just got done talking to them and they said they don't know what's going on and that I have to take it to an electrical shop. I find it hard to believe this isn't something relatively easy to fix if it can be diagnoised. Can anyone help narrow the possibilities so I can at least ask the proper questions about service before having to pay their bill for not finding the problem and getting it towed again to an electrical shop. If you need more info, let me know, I'll do my best. THANKS!

I just remembered that the week before vacation, the car did have a problem starting after driving. What happened in that brief instance is exactly what it's doing now....except now it's permanent.

probably a computer issue. Probably blew a fuse. Check your BCM/PCM fuse. Hope this helps.

Am not sure, but could possibly be an alternator as well.

I have a 2003 SS as well. Did the cruise work prior?? how about the radio or the Information center. It sounds weird but, loosing cruise was the start of a long line of problems. Turned out to be the wiring harness that goes thru the steering column. Hope this might help

Gm has had serious problems with the batteries leaking acid down inside the battery cables and rotting them out from the inside out. I went through 3 batteries the first 4 years that I bought my new Silverado until I figured out what was going on.