Question First: Would a new Diagnostic Module (DM) literally be programed by MB for MY car (from my VIN or otherwise), or is this simply a plug-in with all of the same part numbers being the same and interchangeable?

Background Second: Some months ago I had my first check engine light. Made the trip to my MB dealer and they plugged it in and diagnosed a bad Diagnostic Module. I was told $1,300 part, specially programed in Germany specifically for "my" vehicle. OK, but not today at that price.

Recently, out of curiosity, searched Ebay and there's my DM part number for sale. My MB dealer suggested the "handcrafted" version of the story, while the existence these parts for sale by high-positive-feedback dealers on Ebay, suggests the "plug and play" version of the story. What's the reality here?

Caveat: Of course I'm aware of the inherent risks of buying old junkyard electronics, but if the part is interchangeable, it's certainly worth looking into other alternatives to the dealership. N'est Pas?

i just went through a battery drain issue on a 94 and replaced all the modules with the same from a donor car. no issue with coding on any of them. it's probably a reflex reponse from the dealer that says it needs coding. any module after 94, it seems, needs to be coded. good luck, chuck.