Every transmission has a Vehicle Speed Sensors that is on the left-hand side, slightly above the driveshaft drive flange. This device is used to measure the rotational speed of the final drive part of the transmission and converts this value into an electronic signal that goes to the speedometer module located in the instrument panel. The engine management system ECU also uses the signal in certain models. The first thing to do is to use the handbrake, raise the front of the car, and place it on axle stands. The second step would be to disconnect the wiring of the switch, press the retainer and turn the Vehicle Speed Sensors, and then take it out of the transmission, taking care not to break the delicate electronic parts. Obtain the O-ring seal or gasket. To refit, invert the take-off process with a replacement of the O-ring seal or gasket.