my 99 cummins 24v 4x4 wont shift into overdrive, shifts 1st-3rd perfectly then stays there, need some hints, got codes: P1693 Mil Flt in companion module??? and P1682 voltage, and P0720 speed sensor

 

When was the last time you had your tranny serviced? Do you have a torque lock switch?

Did this happen one day to the next or did it start off everyonce in a while and now it doesn't upshift anymore?

C

 

bought the truck with a blown trannyline fixed the line and put all new oil in it and it shifts perfectly 1st-3rd and then stays in third but when i had the scan tool on it when i drove it the scan tool said that it shifted into 4th when it really was still in 3rd.

 

solved the proplem...... od was cooooked we rebuilt the od and now it is mint