As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING THE CARGO FIRE DETECTION CHECK THE FORWARD ARM LIGHT WOULD NOT ILLUMINATE IN THE NORMAL POSITION. VERIFIED DISCREPANCY. BITE TESTED FWD CARGO ELECTRONIC UNIT REF MM 26 16 00 801. FOUND FAULT FOR DETECTOR B 2. REPLACED DETECTOR B 2 REF MM 26 16 01 000 801 AND 26 16 01 400 801. OPS TEST OK PER MM 26 16 00 710 801.