The ECAIS systems you saw flash were the original cause of some sort of electrical problem. EQUIP COOLING OVRD is the automatic reconfiguration of a B777's Electrical Equipment bay ("MEC") which commands a vent to open to outside ambient air sucking smoke or electrical fumes from the MEC. This also draws air pressure from the cabin.
It exposes the cabin supply ducts to ambient air pressure therefore is also designed to inhibit and silence cabin pressure alarms. The MEC vent will normally close once smoke is no longer detected.
Worth noting too that whilst the MEC has fire and smoke detection there is no fire or smoke alarm provided to pilots except in the Cargo Freighter version of the B777