Ok, I just purchased a 2003 Tahoe LT Z vin. The key fob worked perfectly for the first week and then nothing. I replaced the battery and still nothing. I then got a new remote and tried programming it......still nothing. It will go into program mode but acts like its not receiving signal from the remote. The only other thing is it has an after market plug N play crime stopper remote start. That too has quit working. I have checked all fuses and visible grounds. Can anyone point me in the next right direction? If you open the doors after its been locked the factory alarm will sound so its still working in that aspect. Thank you in advance for any help.

 

A couple of things. When you replaced the battery in the fab, did you break or loosen the solder points where the battery makes connection with that holds the battery in. A common problem with these fabs. If they are loose or broken, a small drop of solder will usually fix them. If you have the old one you might be able to fix it. I think autozone or advanced auto has a machine to test the fabs to see if they are working or not.
Since you just got it, the remote control door lock receiver (rcdlr) might be full of slots from previous fabs that got programmed and the old ones never got deleted. That could be why it wouldn't program, no more empty slots. I think the only way to check if there are open slots is with a factory tech 2 scan tool, dealer only.
The remote start might be related or not. But I would remove it to cross it off as a possible source. That's what the dealer would do. But I don't think it's related but you never know who or how they installed it.
hope this helps

 

OK Update. I took it to the dealer and they said the Passenger door module Isn't programming the fobs. They said there is either a broken wire somewhere or the module is bad. I might swap one out from the junk yard soon. Any other thoughts? The fobs are working, they tested those. The module is going into program mode but not communicating with the remotes.