As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: BOTH PILOTS SMELLED TOXIC FUMES- MUSTY ODOR FOR MOST OF FLIGHT. MAINTENANCE ISOLATED THE SOURCE OF THE ODOR TO THE APU. **ORIGINAL REPORT WAS AALA202305156778** MAINTENANCE FOUND THE APU OIL FILLER CAP LEAKING OIL AND THE APU FUEL CONTROL UNIT LEAKING OIL. (AALA202306267794) MAINTENANCE REPLACED THE OIL FILLER CAP AND THE FUEL CONTROL UNIT. A SATISFACTORY LEAK / OPERATIONAL CHECK WAS ACCOMPLISHED.