Overdrive Switch: Description and Operation

DESCRIPTION
The floor-mounted transmission range selector lever includes a transmission control switch in the gearshift lever knob. The transmission control switch (TCS) is a momentary contact switch.

OPERATION
^ 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. The PCM energizes the transmission control indicator lamp (TCIL) when the switch has been pressed to cancel overdrive. The TCIL indicates overdrive cancel mode activated (lamp ON) and electronic pressure control (EPC) circuit shorted (lamp flashing) or monitored sensor failure.
^ The system automatically engages into the OVERDRIVE mode each time the ignition switch is turned to RUN.
^ Pressing the transmission control switch with the ignition switch in RUN locks out the OVERDRIVE mode (fourth gear). Pressing the control switch once again permits the transmission to shift into the OVERDRIVE mode (fourth gear).