As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TAXI OUR, COCKPIT BEGAN FILLING WITH SMOKE SHORTLY AFTER RECEIVING APU LOW OIL MESSAGE AND APU AUTOSHUTDOWN. COMPLIED WITH QRH. INSPECTED AND FOUND APU FAILED AND CONTAMINATED COALESCER SOCKS. REMOVED AND REPLACED LT AND RT COALESCER SOCKS. RAN BOTH PACKS NO ABNORMAL ODORS. PLACED APU ON MEL.// REF 180677/1 - REMOVED AND REPLACED APU ASSY ON W/O 137202, RAN ENGINES AND PACK TWICE ON GROUND, NO SMOKE NOTED. (K)