Transmission Control Switch (TCS)
WARNING: This page is about a different car, the 2007 Mercury Mariner and 2007 Ford Escape. 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. When the TCS switch is pressed, a signal is sent to the PCM. The PCM then energizes the transmission control indicator lamp (TCIL) and engages or disengages 4th gear operation and provides coast braking in 2nd and 3rd.