What condition will prevent the FMS from autotuning?

The condition that prevents the FMS (Flight Management System) from autotuning is when there are green needles displayed. This occurs because green needles indicate that the aircraft is in a state where it is ready to follow an autopilot mode but is not actively seeking to tune its navigation systems to the most optimal frequencies or waypoints.

In contrast, when the FMS is receiving or processing other relevant information or conditions, it may allow autotuning to function. The other options, such as being in manual mode or excessive speed, do not directly impact the FMS's ability to autotune in the same manner, while blue needles typically indicate that the system is in a different operational state that still allows for autopilot functions. Recognizing the state indicated by the green needles helps pilots understand when the system is ready for manual intervention rather than automation through autotuning.