Pattern Select Switch Snow Mode Circuit [12/2013 - 11/2016]: Description
WARNING: This page is about a different car, the 2016 Toyota Highlander, 2015 Toyota Highlander, and 2014 Toyota Highlander. However, it is still accessible from the selected car via links, so may be relevant.
When SNOW mode is selected, the operation of the throttle motor is moderated to control engine output. This helps to reduce skidding of the drive wheels, and assists with takeoff acceleration, driving straightness and turning stability.