Cranking Holding Function Circuit: Description
WARNING: This page is about a different car, the 2008 Toyota Yaris. However, it is still accessible from the selected car via links, so may be relevant.
The cranking holding control system provides a current to the starter when the ECM detects the ignition switch's start signal (STSW). When the ECM judges that the engine has started, the system cuts the current to the starter. When the ECM receives the STSW signal, it turns on the ACC (Accessory) relay, which prevents flickering of the combination meter, clock and audio system. Also, the ECM sends a signal to the ECM's STAR terminal. Then the STAR output signal travels through the Park/Neutral Position (PNP) switch to the ST relay, causing the starter to activate. When the engine is cranking, the starter operation signal is sent to the ECM's STA terminal.