A machine powertrain includes an engine operably connected to a torque converter and a transmission. A switch associated with the torque converter provides a locking signal indicative of a locked or unlocked condition of the torque converter. A throttle sensor associated with the throttle provides a throttle signal. An electronic controller receives the locking signal and the throttle signal, and controls operation of the engine at least partially based on the throttle signal and the locking signal. The electronic controller determines whether a locked or unlocked condition of the torque converter is present based on the locking signal, determines whether a part throttle operating condition or a full throttle operating condition is present based on the throttle signal, and selects a derated power curve when the part throttle operating condition is present and when the torque converter switches from the unlocked to the locked condition.