As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMBOUT LEFT ENG FIRE DETECT LIGHT CYCLED ON AND OFF, OCCASIONALLY THE LT ENG FIRE T-HANDLE CAME ON AND OFF A FEW TIMES. AIR RETURN TO DTW. MAINTENANCE FOUND SENOR LOOP CHAFED, INSTALLED SERVICEABLE SENOR LOOP P/N 472326 IAW SF-340 MM 26-11-05-2. ALL CHECKS GOOD.