Output Shaft Speed (OSS) Sensor
WARNING: This page is about a different car, the 2007 Lincoln MKX and 2007 Ford Edge. However, it is still accessible from the selected car via links, so may be relevant.
The output shaft speed (OSS) sensor is a hall effect pickup, located at the output shaft ring gear, that sends a signal to the powertrain control module to indicate transmission output speed. The OSS is used for torque converter clutch control and shift scheduling.