Rear door lock question

[hendedo]

Hello all. 03 Z71 tahoe, 5.3L 105 K miles, all stock.
This is our door lock problem. Driver door lock / unlock with the fob fine.
Passenger door lock / unlock with the fob fine.
Rear doors and lift gate rarely unlock after MANY attempts. How can just these three doors act different fron the front doors?
The lift gate is very important to unlock as my dogs ride back there.
We took the trim panel off and I worked the lock assembly by hand and lubed it. It works with no issues. It is not getting a signal from somewhere.

Where can I buy a switch for this or is it tied to the switched for the rear doors and do I need three?

Thank You for helping us with this. Don.

 

[ScottyBoy]

Does it act the same with the power doorlock switch? or does it only do this with the key fob?

 

[hendedo]

Thanks for the reply. Yes, the same with the switch on the door as well as the fob.
We have not figured why just the two rear doors and the lift gate do this inconsistent unlocking. When the DO finially unlock, all three are unlocked. This is why we wondered if they were 'linked' together somehow.
We don't want to just throw parts at it ($$$) to see how it fixes it.

Thank you for the reply.

 

[ScottyBoy]

Yes, the 3 rear doors are linked together. The two front doors each have a "door module" in them that powers everything in that door. The "module" is basically the box with the window switch. The locks, mirrors, heated seat buttons, door panel lights, they ALL plug into the window switch or "Driver's door Module". The module in each front door communicates back and forth over the databus, so when the unlock signal is sent to each module, the module unlocks each front door. The rear doors dont have modules in them, so they must have relays somewhere.