Does the 2015 Toyota Sienna use power steering fluid?

No, Your 2015 Toyota Sienna doesn't use any power steering fluid, so there's no way You can check the level. Instead, it uses an electric power steering system (EPS). This makes use of an electric motor instead of a hydraulic system, so there's no fluid involved there. But, things can still go wrong. You may encounter the steering being slow to responded, as well as being very stiff, or, conversely, very loose. And, since it's electric, You can lose the assisted steering altogether with an electrical failure, or even a software flaw with the ECU. Costs to repair with this system aren't cheap either, with the cost of a power steering control module running almost to a thousand dollars, depending on what You get, and labor hitting almost $140 to get it installed.