My '04 has this code also. Shifts but doesn't go into overdrive was told it may be an output speed sensor? Any info would be helpful.

 

Getting this code on an '05 -3500 4x4. Owner seems to think its Biodiesel related. My scan tool can't erase the code, but owner isnt noticing any drivability issues. UpShifting and Downshifting very well. Any suggestions on where I should start on this?