Vehicle Speed Sensor
WARNING: This page is about a different car, the 2000 Lexus SC 400, 2000 Lexus SC 300, 2000 Lexus LS 400, 2000 Lexus GS 400, and 2000 Lexus GS 300. However, it is still accessible from the selected car via links, so may be relevant.
Instrument cluster senses when microswitch contacts inside speed sensor open and close (4 times per revolution). ECM receives speed signal from instrument cluster.