rear door locks/tailgate don't lock

[nycdesignkid]

Hello,

I have a 2003 GMC Yukon. I noticed recently that my 2 rear doors and the tailgate do not lock. I tried both the remote and from inside the car w/ the drivers switch. I can lock the 2 rear doors manually, but unfortunately there is no way to ever lock the tailgate. All 4 of my doors do unlock though. Now...at one time (about 2 1/2 years ago)I did have a Clifford remote start/alarm installed which later created problems with manual starting of the vehicle. I brought it to GM and they said the alarm was conflicting with the stock alarm and therefore was not able to start the vehicle. So I removed the clifford "brain", took the car back to GM and they said everything was o.k.....I'm not sure, but the door lock issue could be dating all the way back to when I removed the al;arm brain??!! Do you have an idea of what could be wrong? Perhaps there is a plug that I didn't reconnect or something? If you do believe it is wire related...could you please explain which wires may be the problem, and what I can try to do??? Thank you VERY much!!

Tom

[GM-Tech]

There are separate lock and unlock relays for just the rear doors. Since the doors unlock, it could just be a bad lock relay. It's in the fuse block on the left side of the dash.

 

Just swap the two relays and see if the problem changes to locking okay, but not unlocking.