Overdrive Switch: Description and Operation

On vehicles equipped with an automatic transmission with overdrive, the engine controller uses the overdrive solenoid to control the 3-4 overdrive upshift. The overdrive override switch is located in the instrument panel.

When the overdrive override switch is closed, the transmission is allowed to enter overdrive if all conditions are met. If the switch is opened, by the driver pressing it, the transmission will not be able to enter overdrive.

The overdrive override switch circuit contains two other switches; a transmission thermo-switch and a coolant temperature switch. If any of the three switches is open, the transmission will not be able to enter overdrive. If any of these switches is opened while the transmission is in overdrive, the transmission will shift down out of overdrive.