As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SEA - OIL SMELL COMING FROM AIR VENTS. AIRCRAFT WAS ON DESCENT INTO SEA WITH ENGINES AT IDLE POWER FOR 10 MIN. CREW DETERMINED SMELL WAS FROM THE APU. REPLACED APU IAW MM. APU OPS CHECKED GOOD ON GROUND RUN. AIRCRAFT RETURNED TO SERVICE.