What does a steady green light indicate when the EXT PWR is on?

A steady green light when the EXT PWR is on indicates that the external power source is connected and functioning properly. This signal confirms that the aircraft is receiving stable and adequate power from the ground supply, which is crucial during pre-flight checks and ground operations. Proper external power ensures that all necessary systems and avionics remain operational without draining the aircraft's batteries.

The other choices refer to different conditions that do not apply when the steady green light is illuminated. No issue detected with external power is a broader statement that doesn't specifically pertain to the light status, while system shutdown mode and battery power transfer relate to different operational states that would not be indicated by a steady green light. Thus, the presence of this light specifically denotes a reliable connection to external power.