Throttle Actuator Control (TAC) System Description: Notes
The engine control module (ECM) is the control center for the throttle actuator control (TAC) system. The ECM determines the driver's intent based on input from the accelerator pedal position sensors, then calculates the appropriate throttle response based on the throttle position sensors. The ECM achieves throttle positioning by providing a pulse width modulated voltage to the throttle actuator motor. The throttle blade is spring loaded in both directions, and the default position is slightly open.
The throttle body actuator contains a contact-less inductive blade position sensing element that is managed by a customized integrated circuit. The throttle body actuator position sensor is mounted within the throttle body and is not serviceable. The ECM supplies the throttle body with a 5 V reference circuit, a low reference circuit, an H-bridge motor directional control circuit, and an asynchronous signal / serial data circuit. Asynchronous means communication is only going from the throttle body to the ECM. The throttle body cannot receive data from the ECM over the signal / serial data circuit. The throttle body actuator position sensor provides a signal that changes relative to throttle blade angle. The customized integrated circuit translates the signal based position information into serial data using the Society of Automotive Engineers (SAE) J2716 Single Edge Nibble Transmission (SENT) protocol. The throttle body actuator position sensor information is transmitted between the throttle body and the ECM on the signal / serial data circuit. The ECM decodes the serial data signal and the throttle position information is displayed on the scan tool.