One problem related to hydraulic power assist steering system 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.
Power steering rack failure on 2004 vehicle with 36,000 miles. Steering is erratic and odd feeling. Concern is that a total ps failure could occur making van very difficult to control.