99 tahoe erratic door locks

Hello,

I just picked up a 99 tahoe to replace my 93' blazer. The problem I have found on the tahoe is that at times, the door locks will just lock/unlock while driving down the road. It does this a few times, then the power locks just quit. I was thinking the door lock relay, but i am not sure. Any ideas? For example, this morning it did this to me, the door lock switch quit working, I can click the keyless remote and hear a relay inside the truck, but the door locks are not moving.

Thanks for the help,

Nate