99 yukon security system

I just purchased this vehicle a month ago and now am having problems with the security system. It seems like it wants to go off in the middle of the night and I can't figure out why. I have changed the batteries in the vehicle and in the F.O.B. and nothing seems to have helped. Please someone help me with this before I spend way too much money by taking it to GM itself. May be a simple fix but I am not a mechanic or so inclined so please help. thanks

Inside the center console is whats called the Body Control Module. It controls everything on a yukon. I have a 99 Denali and sometimes my doors will unlock on its own in the middle of the night. I have a list of problems because of this module. Its a dealer item and is pretty costly. I think mine went bad, because its located right under the cup holders and if something spills...? Have your BCM checked!