Transmission Control Switch (TCS)
WARNING: This page is about a different car, the 2008 Ford Expedition EL and 2008 Ford Expedition. However, it is still accessible from the selected car via links, so may be relevant.
The transmission control switch (TCS) is a momentary contact switch that is located on the end of the column selector lever or on the floor selector lever knob. Pushing the TCS will either disengage or engage the overdrive function of the automatic transmission. If OVERDRIVE is disengaged, the word O/D OFF will illuminate on the instrument cluster and forward gears 1 through 4 are available. The overdrive cancel feature resets after the ignition switch is cycled.