Chrysler Repair: 2000 town & country shift error / transmission, transmission control module tcm, chrysler vans

Question
QUESTION:
2000 town and country Lxi 3.8
The vehicle is shifting out of gear when put into drive. Sometimes it goes
to reverse, park or neutral. The problem is intermittent and getting worse,
but the computer is  not recognizing any problems (check engine). I
haven't checked for codes because it hasn't lit up.
I am thinking it is the transmission control module (tcm) or the solenoid. I
was hoping you would explain symptomatic issues for both, or know of a
different conclusion.
If it is the tcm, can the module be pre-programmed for my vehicle or does
the dealer have to do it? I looked at a rebuilt one for $200 and it
mentioned programming VIN# and updates. Can I pull one of a parts car
or does it need programming?
Thanks for your time.

ANSWER: Hi Ian,
I would begin by checking the shifter cable and housing where it connects to the vertical shift rod at the transmission. It could be something simple there or at the other end in the cabin. There is a switch inside the transmission (transmission range sensor containing 4 switches) that actually senses the position of the vertical shift rod's rotation, and that would be the next bet. It has 4 wires to the tcm which could be checked for continuity/short to ground. The switch grounds one or more of those wires depending upon which position it is set to.  The switch can be replaced without removing the transmission but the pan has to be dropped and the valve body removed. If you have a volt-ohm meter or continuity tester I can give you the readings to expect.
A fault code readout using a plug-in reader would be worth a try, and that can usually be had for free at an Autozone parts store. I wouldn't think it is the tcm at this point, so don't waster your money until you have checked out the other possibilities.
Roland

---------- FOLLOW-UP ----------

QUESTION: I have been looking for other similar complaints and have found several
stories of runaway chrysler vans when idling in park. However, they do not
have solutions and dealers are clueless. I asked a different all expert
(Kevin) yesterday and he said it was outside his expertise. should I file a
complaint with the dealer/manufacturer? This seems like a serious safety
issue for an electronic shifter. I should be able to be confident that my car
will stay in park when idling.

Answer
Hi Ian,
I can only suggest that you take a look at the items I listed. The shifting also has a mechanical component (otherwise why put it inside the transmission, for example the P position engages a mechanical brake on the drive shafts. But if the shift lever in the cabin is not properly adjusted via the cable to the vertical shift rod anything can happen. The internal range switches can impact the solenoids valves, but if you are in Park it shouldn't 'run away. Of course things to wear out. No recalls that I have heard about.
Roland