As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SMOKE ENTERED CABIN UPON SELECTING APU BLEEDS ON. BOTH ACM'S OPERATED AT TIME OF EVENT. RAN ACFT WITHOUT APU BLEEDS AND HAD NO SMOKE. RAN APU, NO SMOKE. RAN AFT ACM (CABIN). NO SMOKE. RAN FORWARD ACM (FLIGHT COMPARTMENT) NO SMOKE. RAN BOTH ACMS, NO SMOKE.