As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PIC REPORTED WHEN APU STARTED AND ACM COMMANDED ON THE COCKPIT FILLED WITH SMOKE. COMPLIED WITH REMOVAL AND REPLACMENT OF AIR CYCLE MACHINE TURBINE. UPON FURTHER INSPECTION FOUND NO FURTHER DAMAGE TO AIRCRAFT AND PILOT REPORTS NO INJURIES TO CREW.