As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FA REPORTS DIRTY SOCK ODOR IN AFT CABIN. ACFT AT GATE JUST PRIOR TO PUSH BACK WITH APU ON. FOLLOWED NO GO PROCEDURES. FOUND APU INLET WITH EXCESSIVE GRIM BUILDUP. CLEANED INLET IAW AMDS 1916-2001. RAN APU BLEED WITH PACKS ISOLATED & TOGETHER USING CABIN AIR SNIFFER EQUIPMENT. FOUND NO ODOR & VALVES WITHIN LIMITS. LEVEL B INSPECTION COMPLETED.