What was found
FLT#1569, CUN-LAX. 'DESCENDING THRU 13,000 ON APPR. TO LOS ANGELES, VERY STRONG 'DIRTY SOCK' SMELL IN COCKPIT PERFORMED FCOM ISOLATION PROCEDURE ON PACK ONE; PERFORMED LEVEL B ECS DECON PER AMM 21-00-00-615-803. NO ODORS DETECTED. A/C OK FOR SERVICE. NO CREW ODOR REPORT FILLED. AP SUSPECT APU BLEED AT FAULT PLACED ON MEL REF L/P 3870098-1.'