Electronic Throttle Body Throttle Actuator Control (TAC)

The electronic throttle body TAC has the following characteristics:

• The electronic throttle body TAC is a DC motor controlled by the PCM.
• An internal spring is used to return the throttle plate to a default position. The default position is typically a throttle angle of 7 to 8 degrees from the hard stop angle.
• The closed throttle plate hard stop is used to prevent the throttle from binding in the bore. This hard stop setting is not adjustable and is set to result in less airflow than the minimum engine airflow required at idle.
• The required idle airflow is provided by the plate angle in the throttle body assembly. This plate angle controls idle, idle quality, and eliminates the need for an IAC valve.
• There is one reference voltage and one signal return circuit between the PCM and the electronic throttle body TAC. The reference voltage and the signal return circuits are shared with the reference voltage and signal return circuits used by the accelerator pedal position (APP) sensor. There are also two throttle position (TP) signal circuits for redundancy. The redundant TP signals are required for increased monitoring reasons. The TP1 signal has a negative slope (increasing angle, decreasing voltage) and the TP2 signal has a positive slope (increasing angle, increasing voltage). The TP2 signal reaches a limit of approximately 4.5 volts at approximately 45 degrees of throttle angle.