As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING CLIMB AT FL120, APU FIRE LIGHT AND BELL ILLUMINATED. APU FIRE DRILL CARRIED OUT, REMAINED (ON). DECLARED EMERGENCY, RETURNED TO AIRPORT WITHOUT INCIDENT. UPON INSPECTION NO FIRE DETECTED. MAINTENANCE FOUND (FIRE WARNING) WIRE NR W272-607-18 SHORTED TO GROUND. WIRE REPLACED, FUNCTIONED CHECKED SERVICEABLE IAW MM 26-15-01. (TC NR 20070202004)