What code requires an action to reset the fault?

The correct choice is fault code, which specifically designates conditions that require attention and action to rectify. Fault codes indicate a malfunction or an issue that impacts the safety or functionality of a system, necessitating a reset or corrective measures to return the system to normal operation.

When a fault code is triggered, it typically suggests that a component or system is operating outside of its intended parameters, which could pose a risk of failure or operational issues. Therefore, addressing the fault indicated by the fault code is crucial for maintaining the system's integrity and safety.

In contrast, warning codes generally serve to alert operators of potential issues that may not require immediate action but should be monitored. Caution codes indicate that there are lesser issues that should be looked into but don't require immediate intervention. Shutdown codes imply that the system is in a safe mode and will not operate until certain criteria are met, but these do not necessarily require an immediate reset as fault codes do.