Diagnostic code for dodge caravan 1996 P1784?

The code is about the switch that monitors the hydraulic pressure for operating the low/reverse clutch of the transmission. That clutch is called into play for all forward gears as well as reverse, so it seems reasonable if that clutch were not working that the car wouldn't move in any gear. I would begin by making sure that there is sufficient trans fluid by inspecting its dipstick. If needed only use ATF +4 but don't overfill it. Also, just on a chance, take a look underneath to see if you see any motion of either the left or right half axles (or one moving, but one not) which would be another reason for no motion due to a drive shaft disconnection or some such anomaly. Other than that, your problem could be with the Low/Reverse solenoid switch in the solenoid pack portion of the transmission (the box on the driver's side of the trans) being stuck. That can be repaired without removing and rebuilding the transmission so let us hope that may be the cause. I would have the car towed to a good independent trans shop that has a reputation for knowing how to service the Chrysler electronic transmission.

Hope this helps.