is it overdrive not working or is it the o/d light not working?
Its a bit confusing - the light indicates O/D OFF.
normal is Light OUT = O/D ON
The o/d button puts 12v thru to select o/d off, the 2 wire cable from the gs stick sometimes breaks where it hinges, which means cant select o/d off.
If you aren't into towing you generally dont need o/d off so ignore it.
If you aren.t going into o/d (with warm engine) it may be the solenoid, or the temp sensor.
enri, June 2016