As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU COLD SOAK START FAILED THREE ATTEMPTS FL 410 -55 SAT. PERFORMED APU ECU BITE TEST IAW AMM 49-61-05. NO FAULTS NOTED AT THIS TIME. VF OPENED DMI# 117364. APU COLDSOAK START ATTEMPT SUCCESSFUL ON FIRST ATTEMPT, DMI CLOSED. ECM 2019P-392 TO ISSUED BY PP ENGINEERING.