Throttle Actuator Control (Tac) System

POWERTRAIN CONTROL MODULE
The PCM determines the drivers intent and then calculates the appropriate throttle response. This information is sent to the TAC module through a dedicated serial data line.

MODES OF OPERATION NORMAL MODE
During the operation of the 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 PCM updates the learned minimum pedal value.
- Minimum 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 PCM 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 PCM 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 PCM will continue to use the accelerator pedal for throttle control; however, the vehicle acceleration is limited.
- Limited throttle mode - The PCM will continue to use the accelerator pedal for throttle control; however the maximum throttle opening is limited.
- Throttle default mode - The PCM will turn off the throttle actuator motor and the throttle will return to the spring loaded default position.
- Forced idle mode - The PCM will perform the following actions:
- Limit engine speed to idle by positioning the throttle position, or by controlling the fuel and spark if the throttle is turned oft.
- Ignore the accelerator pedal input.
- Engine shutdown mode - The PCM will disable fuel and de-energize the throttle actuator.