I believe when is on is on, and when is off is off. Check owner's manual. If you don't have one copy and paste link below; www.fleet.ford.com/maintenance/owners_manuals
If the light says off then your overdrive is turned off, push the button again and the light will turn off and overdrive will be on again.
OverDrive Off
If the overdrive's off light is on that means it's off. If it is off then the overdrive is on.
It means the overdrive is turned off... it's typically a button on the side of the transmission shift column.
You have probably turned off the overdrive function of the automatic transmission. Look for a small button on the gear selector reachable with your thumb.
Normally the overdrive is allowed , so the overdrive OFF light does not light up When the overdrive is switched off , the overdrive OFF light will light up to let you know that the overdrive has been switched off
On the end of your gear selector lever ( PRN etcetera ) is the transmission control switch . Overdrive is the normally allowed position , but when you turn the overdrive off ( the O/D OFF light will light up just above and to the right of the speedometer and if you have the digital dash it will show " overdrive off " to the right of the speed indicator )
it means the overdrive is not on.
Overdrive is the normally allowed position so you don't see the light on If you turn OFF the overdrive , the overdrive off light will light up or if there is a problem the overdrive off light will flash
Many Ford automobile and pickup transmissions have an overdrive function. Most can be turned on and off with a push-on, push-off switch, . The lighted OD-off or indicates that the overdrive function is disabled, turned off. If, while the vehicle is running, you push the button adjacent to the indicator that says OD-off, you will turn on/enable the overdrive function. When the overdrive function is enabled, the OD-off lighted indicator goes of, and there is no indicator when the overdrive is engaged.
The overdrive is "ON" when the light is "OFF". Notice the light for the overdrive has a slash through it.
overdrive shut off