1992 Dodge Caravan Sensor problem??

I have a 1992 Dodge Caravan with a 3.3L V6. I was driving it the other day and the car stopped shifting into the Higher gears. I read this was "limp" mode and that something could be wrong. I cahnged the fluid and filter in the tranny using ATF+4 and reset the computer by disconnecting the battery. The car now starts and runs better but still will not shift to the higher gears. I did the "key dance" to find the codes and it said Code 15, speed sensor. The only Problem i have with this is that my speedometer is still working. Do i change the sensor out and see if that is the problem? Or could it be something else still giving Code 15??