I picked up my 03 SS last summer. The key fob has never worked, which I assumed the fob was the issue. But when I finally called the locksmith out to buy a new one, he couldn't get the new one to program. He tried both his laptop software and the manual method through the radio.

Due to the wires in my trunk, I know that the precious owner had some form of aftermarket stereo setup. I "suspect" this may be the culprit in my fob not programming. Could this be a wiring issue somewhere behind the head unit? Or is there somewhere else that I should be looking? Or is this problem not worth the hastle?

 

Did you try reprogramming the old fob before assuming it was bad? Have you tried any of the other options/settings on the radio control panel (like changing which door locks/unlocks on shifting to/from park) to see if you're able to change them? If you can't it may be a problem with the radio wiring or the radio itself.

 

The question is, do you know if any of the fobs are valid for your car? GM made a lot that look a like, but there is a number on the back of the fob housing that you need to match up.
And it could be possible that something was done somewhere in the car to the wiring.

You'll need to source a schematic or location break down of the keyless entry components and trace them out.