This gearbox sensor monitors the rotational speed or position of a shaft inside the transmission housing. It sends a signal to the vehicle's electronic control unit, which uses the data to manage shift timing and clutch engagement. A failed sensor typically produces erratic shifting, delayed engagement, or a loss of gear selection. The sensor threads into the transmission case and seals with an O-ring or copper washer; the sealing surface should be clean on reinstallation. The two-pin connector mates with the vehicle harness, and the sensor body is machined to match the original housing bore so that no adapter or shim is required.