The rear pass side door will unlock but wont lock.. Switch or actuator?

 

There is an aluminum rivet that holds the actuator to the door. It is common for them to corrode or fall out. When you open the door look at the painted part a few inches below the lock mechanism catch, you should see an aluminum rivet about the size of a nickel. If you see just a hole the actuator is flopping around and needs to be rivetd back to the door. Compare both back doors to see if one has the rivet and not the other.

 

Thats exactly what it is.. Thanks. It fell out..