Transmission Control Switch (TCS)
WARNING: This page does not describe the selected car, but rather 32 other vehicles, including the 2009 Mercury Mountaineer, 2009 Mercury Milan, 2009 Mercury Mariner, 2009 Mercury Grand Marquis, and 2009 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.
The TCS signals the PCM with VPWR whenever the TCS is pressed. On vehicles with this feature, the transmission control indicator lamp (TCIL) illuminates when the TCS is cycled to disengage overdrive.