One problem related to tire pressure light on has been reported for the 2005 Toyota Sienna. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2005 Toyota Sienna based on all problems reported for the 2005 Sienna.
Tire pressure warning system on my 2005 Sienna awd (13,000 miles) turned on. Checked pressure in all tires, left rear was below 15 psi, all others were 25 psi (recommended pressure is nte 51 psi). Filled tire to specification tire pressure and light rescinded. Within 5 days, light reappeared with same procedures and results. Took to the dealer. Dealer replaced single tire indicating a nail was found. Within 30 miles, the replacement tire deflated (dunlop, oem run flat tires) on freeway. No tire pressure warning system light illuminated. Air pressure was checked and did not register any pressure, assume 0 psi. Triggered to check tire pressure after hearing a loud popping sound. Tire pressure warning system is not operating as expected and dealer indicates there is nothing wrong and "that's just how the system works". Remaining dunlop oem run flat tires do not retain pressure greater than 25 psi. Dealer says they retain pressure when monitored there. But within 5 days, pressure returns to 25 psi.