Transmission Control (TC) Switch (MKZ)

WARNING: This page is about a different car, the 2009 Mercury Milan, 2009 Lincoln MKZ, and 2009 Ford Fusion. However, it is still accessible from the selected car via links, so may be relevant.

The Transmission Control (TC) switch is a momentary contact switch that allows the driver to cancel operation of overdrive.

The TC switch is located on the selector lever.

When the driver initially presses the TC switch, a signal is sent to the PCM.

The PCM uses the shift solenoids to disengage/disable overdrive operation.

At the same time, the PCM illuminates the Transmission Control Indicator Lamp (TCIL) to notify the driver that overdrive is canceled.

When the TC switch is pressed again, overdrive operation is enabled, the converter clutch is released and the TCIL is turned OFF.

Whenever the ignition is cycled (vehicle shut OFF, then started again), the TC switch is turned OFF and overdrive will be enabled, even if the TC switch had been on when the ignition was shut off.