Trans problem codes and Delay downshift when stopping and speedo show 20 mph

OK guys and gals
I've got a 2002 Chry Town & Country Limited 3.8 auto & AC

Trying to figure out where to start here, I am seeing a few things going on and also a broken mount on the front support that caused some wiring harness rubbers also. Fixed one wire going to the left Radiator Fan that was shorting out on the AC tube off the compressor. There are about 5 or 6 places it's been rubbering because of the mount movement.

Driveability: The engine runs OK when the trans doesn't cause problems. Seem to upshift OK does delay sometime when putting it into gear. I noticed that when you're in gear the speedo says you're going 20mph when stopped, it says that no matter where you stick it except park. I also noticed when coming to a stop it delays downshift to first gears. (But Scanner doesn't show the downshift)

When I had the scanner hooked up I noticed also that it says it's in second gear when stopped like its' in limp mode but it seems to downshift after you are sitting there about 2 seconds even though it doesn't' show it on the screen. plus it still appears to be upshifting too.

I have the following codes
PO700= Just says there are codes
PO731=Gear Ratio Error in 1St Gear
PO720=output speed sensor Circuit
P1790= Fault immediately after shife

PP455=EVAP system large leak
PO442=EVAP system small leak

I'm trying to figure out where to start on this bad boy. I not sure if I have solenoid problems or a wiring problem. It all kinda points the speed sensor with the speedo acting like it is but it could be a short may be causing the problem.

Give me your thought, please...

As Monde said, I would start with the Output Speed Sensor. A check of resistance between Pins 13 and 14 of the Trans Control Module will give you a look at the circuit's condition. Disconnect the connector from the Transmission Control Module and find Pin 13 (It should be a Dark Green/Violet wire) and Pin 14 (It should be Dark Green/Brown). With a mult-meter set to read Ohms/Resistance ( Ω ), touch one lead to Pin 13, and the other lead to Pin 14. A reading of 300 Ω - 1100 Ω is a good reading. If you get anything else, go to the Speed Sensor and disconnect it. Measure the resistance between the two pins of the sensor. Again, a reading of 300 Ω - 1100 Ω is a good reading. If the reading is bad at the sensor, replace the sensor. If The reading is good at the Sensor, But not at the TCM Connector, check the wires between the sensor and module for faults.

Last night I decided to check the gauges just to make sure it was a big part of the problem. It came back with Codes 100.0 and 400.1. I'm not sure what this code 400.1 is I have not found it anywhere yet.

I check the wires and the sensors both input and output they check out OK and so do the wires. While getting to the control for the trans I notices the top of the control case is rusted bad and has pushed open the top edge I can look inside the box. I am wondering if that not the cause of all the problems. If I replace that box does it have to be flashed or does it come preprogrammed?

Alternator failure is a common cause for transmission related symptoms on these.
One of the the tell tale symptoms is the speedometer registering speed when the vehicle is not in motion.
I would disconnect the large B+ cable from the alternator and take it for a short drive.
I have run into this 3 times that I can remember.

Thanks, makes sense, the Input and output generate AC so it could well be the problem, I was wonder what to go after on the speedometer because it wasn't making sense to me why it would say 20mph in all gears but Park. Everything that coding up is AC related. Thank you for the video I may or may not have come across this on my own.

Head out now to check this out.

Well, it looks like that the problem pulled the plug out so it wouldn't change, and test drove it. Speedometer working right, the way it should. Trans worked fine no harsh downshift anymore shifted great, goes to first gear every time I stopped . I was thinking to myself last night when I found what was screw the speedometer up it would also fix the trans problem.

Thanks for the heads up on this it would have taken me a while to find this on my own probably. Wife thanks you too because it's her van...

Nice, glad you got it figured out!
When I worked in the junk yard, one of the mechanics was about to install a second transmission over that alternator problem until I finally convinced him to humor me by unplugging the alternator (which was making a terrible howling should).
There was no way that I was going to pull a second transmission out of a wrecked Pacifica for him when I could hear that alternator, lol.