Each DCM has a different part number, and the proper part can vary by year as well. Be sure you get the right part. You can sign up for the official mercedes Electronic parts catalog (EPC) - it is free, but you need a credit card number to prove you are an adult. See http://epc.startekinfo.com/epc/start.jsp
Please pardon my rudeness in not welcoming you to the forum in my first response. Welcome to the forum!!
You may also find the W220 S-Class Owners' Encyclopedia helpful. http://www.benzworld.org/forums/w220...tart-here.html