Part shop? What do you mean "Part shop"? Jim

Try a slim-jim or take it to a body shop.

Jim what kind of car or truck please

Hi Andrew you have a gear selector fault inside the gearbox your options are to replace the box with a secondhand box. Otherwise find a reputable shop that can rebuild your own. Regards Jim...

talk to a body repair shop as to the best way to solve you problem.

You should have 3 keys & two remotes

You don't want a slim jim to work too well

Need a body shop to come by with the tools

This can be a little tricky since the door is closed. If it were open it would not be that big of a challenge. I would first try using a slim jim to unlock the door, if this does not work by no means should you try to pry it open. But, you can take it to a body shop and have the outside door lock removed or snatch it out yourself. This may cause you to have to rekey the entire car.

Code 21 is the oxygen sensor.. code 12 means the begining of the test. Disregard code 12. It just means you previously disconnected the battery.
55 is end of message. It just means that the test is done and there are no more codes.

All I could find on 34 is this and it doesn't fir your yr.. 34 (1987-1991) speed control shorted or open

http://www.samarins.com/diagnose/checkengine.html

http://forum.chryslerminivan.net/archive/index.php/t-2362.html

I have had two Caravans. a 1993 and 1995.. check your spark plugs and wires.. they can come loose. If you need a new sensor and don't have a lot of money .. go to the wrecking yard.. I look for Vans that were in accidents because that means they were running .. alot of these vans sit because of bad trannys.. beware of one that looks like it has been sitting awhile.. If you are going to do work on your van get a Haynes or Clymer Manual.. This is the first thing I get when I get a "new" used car.. in the past 40 yrs I have rarely taken my cars to the shop if I have the time to work on them myself.. it seems just a normal tune up these days starts at $300 and all they do is change the wires, plugs and cap.. .. Jim

coil packs could be shot

Body shops will attempt to use a "slim jim", but on a door that has had the linkage drop like on yours, knowledge of how the door mechanism looks is invaluable because there will be less places to grab with the slim jim. Subaru or a Japanese auto repair center will have someone that will be able to do this for you if you aren't successful.

A typical slim jim wont do the trick for you.

You need special tools to do the trick. Most tow truck drivers have them.

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/sean_54c3a3dc48a7773c