2002 Dodge Durango won't downshift when coming to a stop. It will if put in neutral or L2. If I leave it in drive, it will shimmy and shake from 15 mph down (just as manual tranny does if you don't push in clutch) and finally shift to 1st gear when nearly completely stopped. It is also throwing a P0138 code, which I know is a O2 sensor. Could the O2 sensor be backfeeding and throwing transmission into not downshifting? I am really getting frustrated. I have changed TPS, Iac, and cleaned everything on the throttle assembly. I have also tried adjusting the TV cable to no avail. PLEASE HELP!

It is 2002 dodge durango with 5.9 engine.

P.S. It runs awesome. Shifts through all gears like a champ. Superb Power.
Just will not downshift.