As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ODOR IN CABIN WITH APU RUNNING. CORRECTIVE ACTION: STARTED APU. WITH APU BLEED AIR ON, NOTICED A VERY FAINT SMELL. REMOVED AND REPLACED THE HEPA FILTER IAW CE680A AMM 21-70-10. STARTED APU AND BLEED AIR. NO SMELL IS NOTED. NO FURTHER DEFECTS NOTED.