Output Shaft Speed (OSS) Sensor
WARNING: This page is about a different car, the 2006 Mercury Grand Marquis and 2006 Ford Crown Victoria. 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 sends a signal to the PCM to indicate transmission output shaft speed. The OSS sensor is used for TCC control, shift scheduling and to determine EPC.