As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UPON CREW PERFORMING FIRE TEST FOR PRE-DEPARTURE CHECK, APU FIRE WARNING HORN CIRCUIT BREAKER POP OUT. FIRE WAS SHOWING PASS. ALL COCKPIT AURAL WARNING AND INDICATION NORMAL DURING TEST. REMOVED AND REPLACED APU FIRE SHUTDOWN MODULE M869, TESTS ARE GOOD, REF AMM 26-15-04/401. THIS CLEARS 2835019. PLACARD REMOVED.