the challenge with OBD-I is that the application followed no clear standard other than
guidelines and minimal requirements. this allowed each manufacturer to use the port
with some differences. so the question, I believe, might include whether Mercedes
designed storage for their vehicles to include storage of information and/or in what
manner to help with diagnostics? I've not been able to find anything after browsing
OBD history and development for the past hour.
You may also want to include checking with the lads over on Euro MB forums may have
insight, e.g.
MB UK