O/D off light
What does it mean when the O/D Off light comes on?
If it did it on its own then there is a problem with the transmission, could be just a solenoid but don’t wait on this cause it could get really expensive very quickly.
The overdrive option in your transmission has been turned off or the vehicle is no longer in over drive. You do need o d on when on the open highway
Could be a switch all the way to trans. Find a reputable trans guy to diagnose it.