Four-Wheel Drive (4WD) Low Switch
WARNING: This page is about a different car, the 2010 Ford Pickup, 2010 Ford F550 Super Duty, 2010 Ford F450 Super Duty, and 2010 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
The 4WD Low switch sends a ground signal to the IC when the vehicle is in 4WD Low. The PCM then receives 4WD Low status from the IC and adjusts the transmission shift schedule accordingly.