When I use the automatic door locks the back rear passenger door locks and unlocks it just makes a loud noise for a few seconds that sounds like it is still trying to lock. Does anyone know what this is or how to fix the problem. It is very annoying to hear.....help

 

it's the door actuater.
I don't know how much they really cost.

 

I have the same issue on the left side passenger door. It'll run you about $100 for an aftermarket actuator, plus labour.

~Cheers~