pre 2000 46re -40F in 2000 RAM 1500 w/5.9L.
Customer brought vehicle in due to high rpm at highway speeds. Tested w/scan tool attached. not shifting into 4th at all. no codes. fluid temp always at -40F.
Temp sensor changed to new design in 2000, tranny has older design sensor indicating 1999 or older, pan has SAE bolts so it may be several years older.
Will the 2000 control module talk correctly to this old tranny?

 

Check battery voltage, I had one not go into OD because of a bad battery.

 

I'm Just going to shoot in the dark and say not it will not command it... But I am not that savvy!!!!!
I do think you have got a P0711 type code on the trans Temp Sensor for "No Temp Rise after start up" ????
But in the 2000.... The 3-4 Solenoid is controlled by the PCM. I would look to see if it is getting commanded and or has voltage to the solenoid pack?
Just my 2 cents