It is an intermittent problem, sometimes when I start the truck, the doors will automatically lock. However, the majority of the time they do not. I have checked all the fuses that I can find and have been searching the forums for the past 2 days looking for some insight on this. Can someone please help me figure this out?

Thanks in advance for all of your help!

 

maybe an aftermarket alarm if so then most likely if one of the doors are open at the same time the truck is started would explain why it doesnt lock

 

All of the doors are always closed, but I have had the door open and it tried to lock; but most of the time it doesn't even try. Also it does have some sort of aftermarket alarm. I'll try unplugging it and see if my results improve.

Thanks for the help!