As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON TAKEOFF ROLL, THE NR 2 ENGINE 'A' LOOP FIRE WARNING ILLUMINATED. THE TAKEOFF WAS ABORTED BELOW 30 KNOTS. THE AIRCRAFT RETURNED TO THE GATE. MAINTENANCE REPLACED THE NR 2 FIRE DETECTION CONTROL UNIT. THE SYSTEM TESTED OK. THE AIRCRAFT RETURNED TO SERVICE.