As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE AIRCRAFT HAD A BRIEF HISTORY OF THE APU FIRE WARNING ACTIVATING DURING FLIGHT. NO EVIDENCE OF FIRE WAS FOUND. TROUBLESHOOTING FOUND APU TAILPIPE DETECTOR CONNECTORS SHORTING TO GROUND. THE CONNECTORS WERE REPLACED. IN ADDITION, THE FIRE DETECTION MODULE WAS REPLACED AS A PRECAUTIONARY MEASURE. OPERATIONAL CHECKS WERE GOOD.