As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
INSPECTION TYPE:ETOP DIVERSION - DURING CLIMBOUT A LEFT ENGINE DUCT LIGHT ILLUMINATED THE CREW RAN THE CHECKLIST CONTACTED DISPATCH, BUT WERE UNABLE TO CONTINUE TO BFI DUE TO ICING CONDITIONS. FLIGHT LANDED WITHOUT INCIDENT IN RFD. REMOVED AND REPLACED LEFT WING DUCT LEAK SENSOR ELEMENT IAW MM 26-18-01-4. OPS CHECK LEAK SENSOR SYSTEM IAW MM 26-18-01-4. OPS CHECK GOOD.