One problem related to power steering pump 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.
At varying rates of speed, on dry roads, my van's vsc and traction control icons will illuminate on the dash, the acceleration will cease and the brakes will pump 2-4 times, and the steering will stick. Originally, this occurred only on roads that curved however the frequency of occurrence is increasing and it now occurs on straight roads as well.