This is the major error code captured at the moment the card actually went down, the fatal-error counterpart to cardDiagNonFatalErrMajor. Because it's captured at the point of the crash, this is the number support engineers ask for first when investigating an unplanned card outage, since it points to the root fault class that took the card offline. For example, cardDiagFatalErrMajor equal to 7 mapping to a watchdog-timeout category tells the admin the card's firmware hung rather than suffered a hardware fault.