A lot of OBD-II scanners won't pull the transmission codes. You'll have to either find a buddy with one of those Snap-On scanners, rent/buy a high-end OBD-II scanner that specifically lists code-scanning capability for transmission codes, or have a dealership pull the codes for ya'.
It could be something as minor as a sensor of some kind throwing off the tranny, since most new automatics are electronically controlled - hell, even a bad plug wire can screw with your shifts, sometimes (it did on the 4.6L Crown Vic, Cougar, and T-Bird that I've owned) - but it might also be something more severe.
Is your "O/D off" light blinking? If so, that's an indication that you've got stored tranny trouble codes.
It could be something as minor as a sensor of some kind throwing off the tranny, since most new automatics are electronically controlled - hell, even a bad plug wire can screw with your shifts, sometimes (it did on the 4.6L Crown Vic, Cougar, and T-Bird that I've owned) - but it might also be something more severe.
Is your "O/D off" light blinking? If so, that's an indication that you've got stored tranny trouble codes.