Idle Air Control Valve: Prius

The idle speed is controlled by the Electric Throttle Control System (ETCS). The ETCS is composed of the throttle motor to operate the throttle valve, the magnetic clutch to connect the throttle motor with the throttle valve, the Throttle Position (TP) sensor to detect the opening angle of the throttle valve, the accelerator pedal position sensor to detect the accelerator pedal position, the ECM to control the ETCS and the one valve type throttle body. The ECM controls the throttle motor to make the throttle valve opening angle properly for the target idle speed. For testing of these components, see THROTTLE BODY  under IDLE CONTROL SYSTEMS.