Idle Speed/Throttle Actuator - Electronic: Testing and Inspection

Idle Air Control System Check

Wiring Diagram:

Step 1 - 4:

Step 5 - 16:

Circuit Description

The aim of the MTIA (Main Throttle Idle Actuator) is to control the idle speed with the throttle body itself. The throttle is motorized for low opening angle (0 °, 22.5 °). The characteristics of the airflow are not the same for low and high opening angles. As a matter of fact, the gradient of the mass air flow function of Throttle Position (TP) sensor is lower for small angles that permits to be more precise during the idle speed control. Out of idle speed the throttle is actuated mechanically by a classical accel cable.
The TP sensor provides a voltage signal that changes in relation to the throttle plate angle. The signal voltage will vary from about nearly 5.0 V at idles to about 0.2 V to 0.4 V at wide-open throttle. The TP sensor is one of the most important inputs used by the ECM for fuel control and other functions such as idle, wide open throttle, deceleration enleanment, and acceleration enrichment.