Overdrive Control Switch
WARNING: This page is about a different car, the 2002 Infiniti QX4, 2001 Nissan Pathfinder, and 2001 Infiniti QX4. However, it is still accessible from the selected car via links, so may be relevant.
Overdrive (O/D) switch sends signal to TCM to prevent transmission from shifting into 4th (overdrive) gear.