Starter Signal 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.
While the engine is being cranked, current flows from terminal ST1 of the ignition switch assembly*1 or terminal STAR of the certification ECU (smart key ECU assembly)*2 to the park/neutral position switch assembly and to terminal STA of the ECM (STA signal).
*1: w/o Smart Key System.
*2: w/ Smart Key System.