Control Module: Description and Operation

The transmission control switch is a momentary contact switch located on the end of the transmission range selector lever knob. When the switch is pressed, a signal is sent to the powertrain control module (PCMX1 2A650) to allow automatic shifts from first through fourth gears or first through third gears only, locking out fourth gear (OVERDRIVE). The powertrain control module then energizes the transmission control indicator lamp on the instrument cluster to indicate OVERDRIVE OFF.