The Vehicle Speed Sensor (VSS) is located on the transaxle and generates a voltage signal when it rotates. This signal is used by the PCM to control fuel, ignition, and transaxle shifting. To check the VSS, disconnect the connector and measure the voltage with a voltmeter. If no voltage, check for an open circuit. To further test, raise the front of the vehicle, secure it on jack stands, and block the rear wheels. Reconnect the connector and back probe with suitable probes. With the ignition on and engine off, manually rotate one wheel while holding the other steady. The voltmeter should display a pulsing voltage between zero and 11 volts. If not, replace the sensor by disconnecting the connector, removing the hold-down bolt, and pulling out the VSS. Replace the O-ring and reverse the installation.