[guyonearth]

These vans, like most, are prone to rear door latch problems. You probably have a corroded latch that can't be released by the lock, or, the lock cylinder itself is corroded. I have seen both conditions. Many people hardly ever open the back doors, which explains why they tend to seize up. Also, when they do seize, it's easy to bend the actuator rods or pop them out inside the door. You may have to pull the panels off inside to get access to the latches. Be sure to lubricate the one on the bottom of the left door, it always rusts solid. Since there is a latch at the top of the left door, many vans end up with a jammed lower latch that just wedges against the bottom sill. If your door seems to not be "hooked" at the bottom when closed, that's probably what's wrong.