Well, the damn gremlins are at it again in my truck - I just started having a strange problem with the power door locks. Sometimes they work just fine, but about 50% of the time only the front doors lock and the rear doors & the tailgate don't. And they always all unlock just fine - it's only the locking that I'm having a problem with, and only on the rear doors, and only sometimes. So for example, I can stand there and click the lock button and all the doors will lock, but then I will unlock them and then click the lock button again and only the front doors will lock. And then I'll do it again and they'll all lock. It is completely random, and it's getting really annoying having to always check my back doors to make sure they are locked. The front doors always both lock & unlock with no problem, it's just the rear passenger doors & tailgate that don't always lock.

My initial thoughts were a bad fuse or relay, but if those go bad isn't all or nothing? Since this is an intermittent problem where it works sometimes but not always, it really has me stumped. Any ideas?? I'm stumped.

 

I haven't had a chance to look into it yet, but I recently discovered that I have the same issue. I wonder how long I have been leaving my rear doors unlocked for??

 

I would suspect an issue with or at the BCM if both the rear doors and the liftgate are affected. Check the Grey C2 connector at the BCM(the box mounted directly below the steering column).

 

That's exactly what I thought when I first noticed it!! I had actually set off my alarm on accident a few times when I opened my rear tailgate and the alarm went off, which I thought was weird because the alarm only goes on when I lock all the doors with the remote. It didn't even hit me what was happening until about a week ago and I hit the lock button and then a friend of mine opened the rear door from the outside, and I was like what the!?!?

 

The rear door lock actuators have a high failure rate, and go out just like you are describing. The next time they are not locking, watch the levers, maybe even touch them if you can. You will probably notice the slightest movement in them, telling you that the actuators are too weak.