There is no OD light "ON"
Just OD OFF light
You may have a faulty switch in the shift arm or shorted wires
There are 2 wires to the switch, one has 12volts the other runs to computer, if the wire to computer gets 12v then OD OFF light comes on, if it gets 12v again then OD OFF light goes off
Pull off the Clam Shell covers from steering column
Look at the base of the shifter arm, you will see the 2 wires coming out of the metal shaft, follow those wires to the connector, unplug it, also just have a look at the wires to see if there are any breaks/chaffing where the 2 wires can touch
This will disable OD OFF light from coming on again, because OD is reset to always on when computer reboots
But OD will be on all the time now
Picture of shift arm with the 2 wires and connector:
https://i.ebayimg.com/images/g/OgYAAOSwZlZaMtv3/s-l400.jpg