Modes of Operation

Normal Mode 

During the operation of the throttle actuator control (TAC) system, several modes or functions are considered normal. The following modes may be entered during normal operation:

• Minimum pedal value-At key-up the powertrain control module (PCM) updates the learned minimum pedal value.
• Minimum throttle position (TP) values-At key-up the PCM updates the learned minimum TP value. In order to learn the minimum TP value, the throttle blade is moved to the closed position.
• Ice break mode-If the throttle is not able to reach a predetermined minimum throttle position, the ice break mode is entered. During the ice break mode, the control module commands the maximum pulse width several times to the throttle actuator motor in the closing direction.
• Battery saver mode-After a predetermined time without engine RPM, the control module commands the battery saver mode. During the battery saver mode, the TAC module removes the voltage from the motor control circuits, which removes the current draw used to maintain the idle position and allows the throttle to return to the spring loaded default position.

Reduced Engine Power Mode 

When the PCM detects a condition with the TAC system, the PCM may enter a reduced engine power mode. Reduced engine power may cause one or more of the following conditions:

• Acceleration limiting-The control module will continue to use the accelerator pedal for throttle control; however, the vehicle acceleration is limited.
• Limited throttle mode-The control module will continue to use the accelerator pedal for throttle control; however, the maximum throttle opening is limited.
• Throttle default mode-The control module will turn off the throttle actuator motor and the throttle will return to the spring loaded default position.
• Forced idle mode-The control module will perform the following actions:
  • Limit engine speed to idle by positioning throttle position, or by controlling fuel and spark if throttle is turned off.
  • Ignore accelerator pedal input.
• Engine shutdown mode-The control module will disable fuel and de-energize the throttle actuator.