Starter Inrush Current Reduction Relay Circuit [11/2016 - ]: Description
WARNING: This page is about a different car, the 2019 Toyota Highlander, 2018 Toyota Highlander, and 2017 Toyota Highlander. However, it is still accessible from the selected car via links, so may be relevant.
The starter inrush current reduction relay prevents the battery voltage from becoming dropping excessively while the starter assembly is operating. If the battery voltage drops below the threshold, stop and start control will be prohibited. In order to prevent this, the engine stop and start ECU operates the starter inrush current reduction relay for approximately 0.1 seconds after the ST NO. 2 relay is activated. By allowing current to flow to the starter inrush current reduction relay, the current that flows to the starter motor is reduced, preventing the battery voltage from dropping excessively.