I don't have my Sienna yet, from the cam side the connector is 5 pin female only 3 wired - see 2nd pic below. My strong educated guess, based upon features present in the OM for the Cam, one lead is ground, one is always on 12V, one is ignition switched 12V - 12V verified by operating voltage from label on back of cam. BUT I don't have a means to verify this without my Sienna. The actual blue connector in the van may have more leads actually wired. If you have a voltmeter and your Sienna test it and post your results.@BearInStPete - can you tell me how many pins for the blue male connector (not-in-used connector tucked under the overhead console) used to connect the OEM dash cam? Someone earlier on mentioned 12 pins, but that doesn't look like one based on the size. Might be wrong, but would be great to get a confirmation.
PS - definitely not 12 pin, that was started by someone referencing an install on a Tacoma connecting to the rear view mirror connector using a third party adaptor - good intentions but incorrect noise in the thread.