How do you reset the anti-theft system in a 2000 Toyota Sienna?

To reset the anti-theft system in a 2000 Toyota Sienna, first ensure that the vehicle is unlocked. Insert the key into the ignition and turn it to the "On" position without starting the engine. Leave it in this position for about 10 minutes until the security light stops flashing and remains steady. Afterward, turn the key off and then start the engine to complete the reset.