Transmission Control Switch (TSC)

The Transmission Control Switch (TCS) is a momentary contact switch that allows the driver to cancel operation of 4th (overdrive) gear.
The TCS is located on the cud of the selector lever.
When the driver initially presses the TCS a signal is sent to the powertrain control module.
The PCM uses the shift solenoids to disengage/disable 4th gear operation and activate the coast clutch.
At the same time the PCM illuminates the Transmission Control Indicator Lamp (TCIL), to note by the driver that 4th gear is canceled.
When the TCS is pressed again, 4th gear operation is enabled, the coast clutch is released and the TCIL is turned off.
Whenever the ignition is cycled (vehicle shut off then started again) the TCS is turned off and 4th gear will be enabled, even if the TCS had been on when the ignition was shut off.