Have a 2004 grand caravan. I ran over the fob any way van wont start now. wen i put the fob bac together it unlocks n locks d drs by its self. Locksmith was able 2 read code of key

SOURCE: 2005 Pontiac SV6 Montana key fob unlocks doors but will not lock

For the sliding doors you need to clean the contacts, there are 6 or 8 on both sides, just wipe them clean as they are probably covered in oil/grease/grime.

SOURCE: 2002 Dodge Grand Caravan Driver Door Lock/Unlock Switch

sorry not sure the 12v prob will help this swtich works on 5v off 3v unlock 1v lock single wire lock/unlock logic signals
I found wiring diagrams at
http://www.dodge.com/bodybuilder/2004/docs/wd/rswd/tc.pdf
it is 2004 but use the wiring diagrams to test the wires
(most likely to fail where they flex)
because it is using logic gates disconnect the plug at each end of the wire you are testing or the damn thing will find a few diffrent ways to trick you.

SOURCE: Car will not unlock.

To get inside the car .... Use the key in the lock cylinder, unlock the drivers door to get inside. You shouldn't have to reprogram the fob unless it or the keyless module was changed. There may be a blown fuse that supplies the keyless control module (check the owners manual for location). or wires that lead into the Drivers door may be damaged ... The keyless module is located inside the drivers door at the bottom behind the door panel ... do the unlock/lock and trunk release switches on the inside of the drivers door operate the locks and or trunk release? If so it is not the fuse ... and not the wires to it ... And it could be your BCM body control module, located in the dash board to right of your gas petal. Because the number entry keypad (code for that is on the inside of the right passenger trunk bracket arm) also doesn't work I assume it's not the key fobs themselves. Your 98 manual is correct for your car.

SOURCE: c240 mercedes key wont turn seems locked

I have a 2001 C240 with the same issue. I removed the positive battery cable from the battery and kept it off for 30 seconds then replaced it. Everything was reset and the key worked.

SOURCE: 2008 Grand Caravan won't start. The lock/unlock

I am having this same issue with my 2008 Dodge Grand Caravan , I had it towed to the local Dodge Dealership. They just told me that it is the Wireless Control Module and it is going to cost $461.00 to replace it.