As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IN FLIGHT, CREW SMELLED DEEP MUSTY SMELL FOLLOWED BY BURNING SMELL FROM ENVIROMENTAL SYS. ISOLATED THE COCKPIT PAC AND SMELL WENT AWAY AFTER ABOUT 5 MIN. REPLACED THE AFT (COCKPIT) ECU IAW MM 21-51-00 AND ALSO REPLACED BOTH WATER SEPARATOR BAGS. SERVICED BOTH ECU'S. STARTED APU AND RAN BOTH PACKS. LEAK CHECK GOOD. RAN COCKPIT ECU FOR 30 MINUTES, OPERATES NORMAL.