driver side back door will not lock automatic

Back door lock will not work with the automatic button. I can do it manual but it will not work with automatic lock. Could this be the solenoid? If it is how do I change the solenoid for just the driver side back door?

I think it is part of the latch assembly.....you remove the door trim, weather seal, linkages, electrical connectors, and then the latch assembly......I think the actuator can be removed and replaced, instead of the whole latch assembly.....

Yes, it is part of the latch assy. Will have a cable on it for the inside door handle also.

Does anybody have a picture of the part I need and where would I buy one at?

http://ecx.images-amazon.com/images/I/41X0PeW6gvL._SY300_.jpg

Looks like that.