As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED. CABIN/APU ODOR TROUBLESHOOT. FOUND APU THE SOURCE OF CABIN ODOR. REPLACED HEPA FILTERS. STARTED BOTH ENG(S) AGAIN WITH EXTERNAL PNEUMATIC AIR RAN BOTH PACKS WITH ENGINE BLEED FOR 10-15 MINS, NO CABIN ODOR/FUMES NOTED.