This read-only field reports the port number (1 through 16, this platform's per-card port range) on the failed slot's card where the circuit failure was detected, narrowing the fault location down to an individual physical port. Combined with circuitFailLocSlot1, this gives an admin the exact slot-and-port coordinate to check cabling or optics on, rather than treating the whole card as suspect. For example, slot 14 port 3 tells a technician to inspect that specific port's fiber connection first rather than every port on that card.