Where is the transmission control module on the 1999 Plymouth Voyager Expresso 3.3L V6

Right fender, inner panel if I remember correctly.

Ill start looking there

car runs good after 30 minutes seems to lose it's power and does not want to change gear properly.

I replaced it on mine it's on the transmission right side looking at the motor there's a 16 pin plug going to it make sure you clean the area well before you take out two 5 in. Bolts and fluid will come out so be ready it's a easy fix