Description of Electric Throttle Control System

Description of Electric Throttle Control System

The Electric Throttle Control System consists of the following.
- Throttle body incorporated with the throttle valve, throttle actuator and throttle position (TP) sensors (main/sub)
- Accelerator pedal assembly incorporated with accelerator pedal position (APP) sensors (main/sub)
- ECM

Operation Description
ECM (5) detects depressed extent of the accelerator pedal based on the signal voltage of the APP sensor (1). Using that data and engine operation condition, ECM calculates the targeted throttle valve opening. On the other hand, it detects the throttle valve opening based on the signal voltage of the TP sensor (3) in the throttle body (2) and compares it with the above targeted throttle valve opening. When there is a difference between them, ECM controls the duty ratio (100% - 0%) of throttle actuator control according to this difference in order to drive the throttle actuator (4) in the throttle body. When there is no difference, ECM controls the duty ratio of throttle actuator targeted maintain the throttle valve opening. In this way, the throttle valve (8) is opened and closed to achieve the optimum throttle valve opening.
In this system, TP sensor and APP sensor have two sensors (main and sub) each to assure highly accurate and reliable control and abnormality detection. Also, when ECM detects an abnormality in the system, it turns off the throttle actuator. When the throttle actuator is turned off, the throttle valve is fixed at the opening of about 22 - 27° (default opening) from its completely closed position by the balance of the return spring and open spring in the throttle body.
This throttle body is not equipped with IAC valve for idle speed control. Idle speed control is operated by the throttle actuator.