Which status symbol indicates a known fault that is not dangerous enough to ground the aircraft?

The appropriate status symbol that indicates a known fault which is not serious enough to warrant grounding the aircraft is the diagonal symbol. This symbol conveys that while there is an issue with the aircraft, it is acknowledged as manageable, thereby allowing for continued operation under specific conditions or with mitigations in place.

In contrast, other symbols serve different purposes: the horizontal dash typically indicates that a system has been checked and is functioning properly, so it does not convey the presence of a fault. The circled 'X' signifies a malfunction that requires attention but does not necessarily mean that the aircraft is grounded. Lastly, the grounding 'X' indicates a serious problem that does necessitate the aircraft being taken out of service until the issue is resolved. This context highlights the importance of the diagonal symbol in maintenance and operations, as it allows pilots and ground crews to understand that the aircraft can remain operational despite existing faults.