i doubt the v6 would be too much different than the i4 tranny wise, so the TCU should be separate.
The FSM should tell you how to do the tranny diagnostic mode.

I'm assuming you've ruled out the possibility of it just being shitty fluid and a bad filter
personal experience, 95% of auto tranny issues start with old fluid and a bad filter. a good overnight drain/drip and some fresh fluid, maybe throw some lucas in there and a new filter usually solves the problem.
I forget how to test the condition of the fluid. my rule of thumb is if it isn't blood red, then it is bad. It'll get a little bit darker after some use, but if it even starting to change from red to brown then its done.