Ok MBDOC,

Then what is part # 2118209126 for. I have a brand new rear SAM and have replaced my siren. I have gotten the part number from my Mercedes Benz dealership with the DAS print out sheet showing the fault. IT IS THE CONTROL MODULE. May be connected to the SAM but it is the module that controls the anti theft alarm.

Go the this website https://www.getmercedesparts.com/oem-Mercedes-parts.html,
and enter this part number 2118209126