Circuit Description
WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The throttle actuator control (TAC) system uses vehicle electronics and components to calculate and control the position of the throttle plate. In order to decrease idle speed the TAC system closes the throttle plate reducing airflow into the engine. In order to increase idle speed the TAC system opens the throttle plate allowing more airflow into the engine. If the actual idle RPM does not match the desired idle RPM within a calibrated time, this DTC sets.