What cause the 2004 Sienna Tie light on .?

The 2004 Sienna is equipped with a Tire Pressure Sensor. The indicator light means at least one of your tires is low in pressure. Also check your spare tire, as the tire light could indicate low tire pressure in the spare (it has happened many times, by the way). Once you check and refill the air in all 5 tires, the light should clear.