I just bought this 2008 1500 Silverado LT, the passenger door lock is not working. The power lock on the door locks the drivers door but the passenger door not even a click. The remote same thing only the drivers door locks or unlocks. So I’m thinking wiring or the actuator is burnt.
Can anyone give me other pointers?

 

Probably the actuator. Take off the door panel and check the actuator and the wiring.

 

I have the same problem with the 1997 GMC Sierra 1500 4x4 I just inherited from my Dad. The passenger door won't even lock manually, when I try to push the lock mechanism down. It just pops back up and doesn't feel like it is actuating anything when moved to the lock position. I'll keep an eye on this thread to see if you get any answers that might also apply to my older truck.

 

Mine is locking manually. Must be a common problem.

 

@dwm the linkage inside the door is loose or broken.