Overdrive Switch: Description and Operation

DESCRIPTION
The Transmission Control Switch (TCS) and Transmission Control Indicator Lamp (TCIL) are located inside the end of the transmission range selector lever. Pushing the TCS will either disengage or engage the overdrive function of the transmission. When overdrive is disengaged, the TCIL will illuminate the word OFF. Each time the ignition switch is placed in the RUN position, the transmission will automatically provide overdrive operation regardless of TCS position the last time the vehicle was running.

OPERATION
The transmission control switch is a momentary contact switch. When the switch is pressed, a signal is sent to the Powertrain Control Module (PCM). The powertrain control module then energizes the transmission control indicator lamp and the coast clutch solenoid, applying the coast clutch to provide engine braking, and cancels fourth gear operation. The TCIL indicates overdrive cancel mode activated (lamp ON), electronic pressure control circuit shorted or monitored sensor failure (lamp flashing).