The 2012 Toyota Sienna has a sealed transmission -- that means that there's no dipstick, nor simple way to check the transmission fluid level. It's supposed to be "maintenance free", but as You know, things rarely are -- from trucks to spouses. With that said, it's recommended that You do a full drain and fill if You're having questions as to the levels. For this, You'll need a handful of tools and a bundle full of patience. Grab a 24mm socket, a 14mm socket, A5mm hex socket or allen key, 5 quarts of Toyota ATF WS, copper wire, a crush washer (recommended), a bottle pump and hose, and a drain pan. You'll need to follow the instructions written out by user ForTech at ToyotaNation -- the link is https://www.Toyotanation.com/threads/the-official-how-to-atf-drain-and-fill.323590/ . Though it's written for the 2nd Generation Tacoma, the instructions too apply to the Sienna.
Ha T.
April 9, 2020
The 2012 toyota sienna has no fluid dipstick in transmission. Those transmission types are designed to be maintenance-free. For check the transmission fluid, your vehicle will possibly have a test valve at the bottom of your car's engine. When the fluid is tested, the car must be level and we therefore recommend having a mechanic with a hydraulic lift or an underground bay to test the transmission fluid. Any fluid leakage should be handled by a mechanic for this form of transmission.
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