Starter Signal Circuit [03/2017 - ]: Description

w/ Smart Key System 

While the engine is being cranked, the ECM detects the current from the ST relay drive circuit to the STSW2 and STA terminals, and carries out engine control when starting (STSW2 signal and STA signal). The ECM drives the ST relay until the engine start signal is input from the certification ECU (smart key ECU assembly), and drives the starter until a complete engine start is detected.

w/o Smart Key System 

While the engine is being cranked, the current from the ST relay flows to the ECM STSW2 terminal. The starter start signal flowing to the STSW2 terminal is mainly used to increase the fuel injection quantity while the engine is starting.