What was found
SFO - ON FLIGHT 2525, RECEIVED L COWL A/I DUCT WARNING MESSAGE. CREW COMPLIED WITH CHECKLIST AND SHUT OFF LT COWL. WARNING MSG EXTINGUISHED. AIRCRAFT WAS RETURNED TO FIELD. MAINTENANCE INTERROGATED MDC AND FOUND NO CURRENT FAULTS. COMPLIED WITH FIM TASK 10-21-00-810-A01. NO LEAKS NOTED. CLEANED CONTAMINATION FROM VENT HOLES. COMPLIED WITH FAULT CONFIRMATION FOR FIM TASK 30-21-00-810-802-A01. NO DEFECTS NOTED. AIRCRAFT RETURNED TO SERVICE. NO PARTS REPLACED.