1. Park your Sienna on a level surface and turn off the engine.
2. Locate the speed sensor. The speed sensor is usually located on the transmission or differential.
3. Disconnect the electrical connector from the speed sensor.
4. Use a multimeter to measure the resistance between the two terminals of the speed sensor. The resistance should be between 200 and 500 ohms.
5. If the resistance is not within the specified range, the speed sensor may be faulty and should be replaced.
6. Reconnect the electrical connector to the speed sensor and start the engine.
7. Drive the Sienna at a speed of approximately 25 mph and observe the speedometer. The speedometer should read the correct speed.
8. If the speedometer does not read the correct speed, the speed sensor may be faulty and should be replaced.
