As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
GROUND CREW REPORTED LARGE AMOUNT OF DARK SMOKE COMING FROM APU. APU PLACED ON MEL. MEL CLEARED BY PERFORMING OPS TEST OF APU IAW AMM TASK 49-10-00-700-801-A. OPS TEST PASSED. THIS CLEARS DEFECT. NO SMOKE OBSERVED COMING FROM APU. COULD NOT DUPLICATE. NO PARTS REPLACED. RETURNED TO SERVICE.