Rear access door switch location on 03 Chevy tahoe

SOURCE: power locks for rear doors and hatch not unlocking

you have two relays on the interior fuse block one for locking and one for unlocking. Swap them and see if the problem is now such that they will not lock. If so you have your answer.

SOURCE: 2006 Tahoe Z71 Rear door will not unlock

The rear door lock/actuator assembly has failed and will need to be replaced. I had one in the shop recently and my tech had to remove the inside trim panel and manually open the rear hatch before it could be repaired.

SOURCE: WHERE ARE THE KNOCK SENSORS LOCATED AT ON AN 03

Knock sensor can be found on top of the engine block, there are two you ´d have to remove the intake manifold to get to them,

SOURCE: power door locks on a 2004 chevy tahoe don't work

The door locks on my 1999 tahoe stopped working and I checked the fuse, which was fine. The problem turned out to be that the fuse for my cigarette lighter was bad and for some reason it also must be working in order for the door locks to work. Put in a new cigarette lighter fuse and the door locks worked again!

SOURCE: 2006 Chevy Tahoe, rear hatch won't unlock

I found this URL on internet http://www.chefseattle.com/blog/site-news/suburban-rear-liftgate-wont-unlock-how-to-fix/ It might fix your problem.