Output Shaft Speed (OSS) Sensor
WARNING: This page is about a different car, the 2003 Ford Windstar. However, it is still accessible from the selected car via links, so may be relevant.
The output shaft speed (OSS) sensor is a magnetic pickup, located at the output shaft ring gear, that send a signal to the powertrain control module (PCM) to indicate transmission output speed. The OSS is used for torque converter clutch control, speed scheduling and to determine electronic pressure control.