Originally Posted by 98LeisureTravelDodge
Should it happen again, check the door auto lock linkage inside the rear door. My 1997 B3500 has a single rear door and the linkage broke, rendering the rear auto door lock inop. It works OK manually. I think the shape of that linkage causes it to be prone to fatigue and failure. I am pretty sure the doors are the same ~1995 thru 2003 (and perhaps earlier).
I bought a 1997 Roadtrek 170P with a rear door that did not electrically lock, but would with the key. After opening up the door panel, I found the link rod was broken in two pieces. Something must have forced it hard enough that it broke the rod, right at a bend. I found there was a similar lock mechanism on ebay with good pictures of the rod, and from that and the two pieces -- I made a new rod out of some steel wire that I had in a junk drawer. Surprisingly, it worked the first time without any further adjustment.
So check ebay if you need a new lock mechanism. It might still be there.