2001 ford expedition overdrive light should it be on while driving or off?

The overdrive light on a 2001 Ford Expedition should be ON while driving normally. This indicates that the overdrive gear is engaged, allowing for better fuel economy at higher speeds. If it's off, overdrive is disengaged, typically limiting the transmission to a lower gear ratio. This is usually done manually by the driver (often with a button on the shifter) for situations needing more power (e.g., towing, steep hills).