Have you been able to figure out the problem? I just bought an 01 Pathfinder with the same exact issue. It will shift from 1st to 2nd smoothly but won't shift to 3rd or OD. I tested with my OBDII scanner and get 2 crankshaft position codes. One code for the sensor itself and one for circuit A. Codes p1335 and p0335.
Would that cause transmission troubles like i explained?