As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMBOUT, PASSING THROUGH 12.000 FT, MAIN CARGO FIRE WARNING INDICATION. NO SMOKE NOR FIRE ON THE MAIN DECK, NOTIFIED ATC AND RETURNED TO DEPARTURE. DURING DESCENT AND APPROACH, THE FIRE WARNING WAS INTERMITTENT. REMOVED AND REPLACED SMOKE DETECTOR UNIT IAW MM 26-10-00. OPS CHECK TEST IAW SUPPLEMENTAL FIRE CARGO CONVERSION PC-0118-06 AND 26-10-00, FOUND NORMAL.