Rear door locks won't work, any ideas?

[Travlinman]

Hi guys, new to the suv world. Picked up a 03 yukon a couple months ago and love it.
Starting to go around and fix all the small things I keep finding and these door locks are next hopefully.

Problem is the rear doors won't lock automatically With either the remote or the front door switch. The front 2 doors lock and work fine but the 2 passengers doors or the rear barn doors won't lock. Everything else works windows,courtesy lights etc.. The p.o had replaced the radio and carpet in the whole car. Could it be something got disconnected under the carpet or could it be with something with the radio wiring? I'm not sure where to look.
Thanks for any help I can get​

 

[scrtcell]

There are relays in the drivers side fuse box that could be bad I would start there they would also affect the rear hatch...

 

[RED TAHOE LS]

Key FOB Battery ??????
David g........

To ad to this problem, GM's of this model possess repeated door lock issues. My opinion is it's rare that both rear passenger + rear doors all quit together. I know that the key fob has to have a STRONG 3.0 Volts to work properly, since the driver door is 1st, then the rest. My Barn Doors are erratic even with clean contacts points. JMHO and good luck