Transmission Speed Sensor (TSS)
WARNING: This page is about a different car, the 1995 Ford Pickup, 1995 Ford F-Super Duty, and 1995 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
TSS (also known as turbine shaft speed sensor) is a magnetic pick-up that sends a signal to the PCM. The PCM uses this signal to determine transmission RPM.