One problem related to tire valve has been reported for the 2004 Toyota Sienna. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2004 Toyota Sienna based on all problems reported for the 2004 Sienna.
2 flat tires within a year on a 2004 Toyota Sienna (tires replaced 2007). Both occasions had a bad valve stem. Both occasions the flat tire warning light came on indicating a flat, replaced valve stems on both occasions. Have since replaced tires due to concern of faulty valve stems.