Chrysler Repair: 07 T & C not shifting under a load

Question
My wife's 2007 3.8l Chrysler Town & Country won't shift under a load. While getting on the interstate running about 30 miles an hour, started to accelerate to merge onto traffic.and it would not shift from 2nd to 3rd. It tached up to three grand I had to let off the Excelerator and let it calm down to 2500 and then it shifted. I get the same identical thing from third gear to over drive. I've clean the wiring harness to the transmission solenoid. I've had a friend of mine put it on his computer and he says the transmission temperature is reading -3°. However it is not bringing up any transmission codes. Can you assist me in this matter thank you.

Answer
Hi Arlington,
The shift rpm pattern is variable and dependent upon the specific internal temperature of the transmission fluid at the moment, so with a clearly erroneous temp reading I would begin with that issue as the possible cause. I assume you have verified the fluid level and you might also want to compare the temps of the 2 hoses that carry fluid to and from the trans cooler.
The temp sensor is internal to the transmission located on the range sensor unit. It is a variable resistor that is temperature dependent. You can measure the resistance across it by removing the plug on the transmission near the shift rod which has 10 pins. Then measure the resistance between pins 3 and 4 of the socket and note how that resistance changes from first start up, to later down the road. The resistance should drop as the transmission warms up. Let me know the results of that set of measurements.
The wire on pin 3 (dark green/violet) connects to pin 34 while the wire on pin 4 (dark green/orange) connects to pin 35 of the #4 plug (black/green)at the pcm. So you could check those connections as well with an ohmmeter while gently shaking the harness.
Please read the PS (below) and respond to it.
Thanks for doing that.
Roland