As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: DURING THE PASSENGER BOARDING PROCESS IT WAS REPORTED THAT THE CABIN HAS A STRONG ODOR THAT SMELLS LIKE DIRTY SOCKS. ALL PASSENGERS AND FLIGHT CREW LEFT THE ACFT SAFELY AND THE ACFT WAS REMOVED FROM SERVICE. SEVERAL FLIGHT CREW MEMBERS EXPERIENCED SYMPTOMS OF DIFFICULTY BREATHING, HEART PALPITATIONS AND NAUSEA. MAINTENANCE DETERMINED THAT THE SOURCE OF THE ODOR WAS THE APU. MAINTENANCE REPLACED THE APU IAW TASK CARD 26L31049003 AND ACCOMPLISHED A SATISFACTORY LEAK AND OPS CHECK WITH NO ODORS NOTED.