O/D OFF Indicator
WARNING: This page is about a different car, the 2007 Lincoln Mark LT and 2007 Ford Pickup. However, it is still accessible from the selected car via links, so may be relevant.
The overdrive (O/D) off function is controlled by the O/D off switch located on the shifter assembly. When the transmission is placed in the O/D off position, the O/D off switch provides voltage to the PCM. The O/D off status is then transmitted to the instrument cluster from the PCM over the communication network.