As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER RUNNING THE APU ON THE GND FOR 7 TO 8 MINUTES, THE CABIN BEGAN TO FILL WITH SMOKE. WE WERE UNABLE TO DETERMINE THE SOURCE OF THE SMOKE. R & R APU WITH AN APU REPAIRED BY MFG. OPERATIONS & LEAK CHECK SATISFACTORY. ALL WORK IAW MM CH 49-11-00. APU CURRENT TIME 7141.0 HOURS. HOBBS READS 28 HRS. INSTALLED PLACARD ADD 7113.