As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PACKS FAILED AND STARTED TO SMOKE AND THE SMOKE ALARM IN THE LAV ACTIVATED. SHUTOFF THE PACKS AND RETURNED TO THE FIELD. RAN LT AND RIT PACKS EXTENSIVELY UNDER VARIOUS ENGINE, APU BLEED SETTINGS. VERIFIED OPERATION OF FLAPPER/RAM AIR DOORS. VERIFIED NO SMOKE COMING FROM BALLASTS/CABIN LIGHTS. ALL SYSTEMS CHECK NORMAL. REPLACED LAV SMOKE DETECTOR WITH NEW UNIT IAW AMM. PN: 0128.