Drive - Overdrive Canceled

WARNING: This page is about a different car, the 2009 Ford Mustang. However, it is still accessible from the selected car via links, so may be relevant.

The D position provides:

activated by pressing the transmission control (TC) switch on the shifter handle.
automatic shifts 1-4 and 4-1.
apply and release of the torque converter clutch.
maximum fuel economy during normal operation.
engine braking in 4th gear.
for cancelling overdrive through TC switch.
illuminates the Overdrive OFF on the instrument panel.