As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT LEVEL CRUISE FROM ATL TO VPS, FL240, THE APU MADE A LOUD POPPING NOISE. THE APU SHUTDOWN AND WOULD NOT RESTART. WHEN THE APU DID RESTART IT MADE THE SAME SOUND. THE IDG WAS DEFERRED SO CREW DECLARED AN EMERGENCY. AIRCRAFT DIVERTED AND LANDED SAFELY IN CSG. MAINTENANCE REMOVED AND REPLACED THE APU ECU. OPERATIONAL CHECKS GOOD. AIRCRAFT RETURNED TO SERVICE. (M)