One problem related to steering rack and pinion has been reported for the 1998 Toyota Sienna. The most recently reported issues are listed below.
Vehicle when turning left such as at an intersection will continue to turn unless the steering wheel is manually returned to the straight ahead position. In other words if you are not paying attention the vehicle will continue to turn and would turn in a circle. This occurs sporadically. When taken to the dealer their repsonse is that Toyota is aware of the problem and that it usually occurs when turning to the right. They are working in the problem. Our feeling is that this is a safety issue and it seems to be getting worse in catching in the left turn mode. Toyota says there is no safety issue. They have been working on this problem for several months or so they say.