Throttle Actuator Control (TAC) System Description: Notes

The throttle actuator control (TAC) system is used to improve emissions, fuel economy, and driveability. The TAC system eliminates the mechanical link between the accelerator pedal and the throttle plate. The TAC system eliminates the need for a cruise control module and idle air control motor. The following is a list of TAC system components:

• The accelerator pedal assembly includes the following components:
  • The accelerator pedal
  • The accelerator pedal position (APP) sensor 1
  • The APP sensor 2
• The throttle body assembly includes the following components:
  • The throttle position sensor 1
  • The throttle position sensor 2
  • The throttle actuator motor
  • The throttle plate
  • The throttle actuator motor relay
• The engine control module (ECM)

The ECM monitors the driver demand for acceleration with 2 APP sensors. The APP sensor 1 signal voltage range is from about 0.6 - 4.7 V as the accelerator pedal is moved from the rest pedal position to the full pedal travel position. The APP sensor 2 range is from about 0.3 - 2.4 V as the accelerator pedal is moved from the rest pedal position to the full pedal travel position. The ECM processes this information along with other sensor inputs to command the throttle plate to a certain position. The throttle plate is controlled with a direct current motor called a throttle actuator control motor. The ECM can move this motor in the forward or reverse direction by controlling battery voltage and/or ground to 2 internal drivers. The throttle plate is held at a 5.7 degree rest position or the un-powered position using a constant force return spring. This spring holds the throttle plate to the rest position when there is no current flowing to the actuator motor.

The ECM monitors the throttle plate angle with 2 throttle position sensors. The throttle position sensor 1 signal voltage range is from about 4.75 - 0.36 V as the throttle plate is moved from idle to wide open throttle (WOT) position. The throttle position sensor 2 voltage range is from about 0.36 - 4.75 V as the throttle plate is moved from idle to WOT position.