What was found
FT # 483, BOS-MEX. DIVERTED TO JFK. DIRTY SOCK SMELL AT 7000'. SMELL DISSIPATED ON CLIMB OUT. CAME BACK CLIMBING THROUGH 20000 VERY STRONG ON DECENT; PERFORMED TROUBLESHOOTING OF CABIN ODOR AND EVIDENCE OF LEVEL 1 ODOR ( DIRTY SOCKS SMELL) PER INFO NOTICE 20A-TO150 . CONFIRMED APU BLEED BEING THE ROOT CAUSE OF CABIN ODOR. MCC ADVISED TO SCHEDULE - ECS .DECONTAMINATION ON NEXT RON. APU PLACED ON MEL 49-10-01. CAT C . MCC NOTIFIED . MX-4 UPDATED .PULED AND COLLARED C/B APU ECBS PLY -L41 AND L42 PER MEL MX PROCEDURES. PLACARD INSTALLED . MDDR # 373115. R & R RE-CIRCULATION FILTER IAW AMM 21-21-41. SUPPLEMENTAL INFORMATION TO FOLLOW.