Cranking Holding Function Circuit: Description
WARNING: This page is about a different car, the 2006 Toyota Land Cruiser. However, it is still accessible from the selected car via links, so may be relevant.
The starter is controlled by the ECM. When the ECM detects a start signal (STSW) from the ignition switch, this system monitors the engine speed (NE) and continues to operate the starter until it has determined that the engine has started (engine speed reaches approximately 500 rpm). If the engine is already running and the ignition switch is turned to START, the ECM will not operate the starter.