Overdrive Switch: Description and Operation

The Transmission Control Switch (TCS) is included with floor-mounted shifter and available on column shifter. It is a momentary contact switch. When the switch is pressed, a signal is sent to the Powertrain Control Module (PCM) to allow automatic shifts from first through fourth gears or first through third gears only, locking out fourth gear (OVERDRIVE). The PCM then energizes the Transmission Control Indicator Lamp (TCIL) on the instrument cluster to indicate OVERDRIVE OFF.