I have taken a look at my WIS to find the right documents as W208 can have many different engines, each with several years of change. The MB name for the ECU is ME-SFI - fuel injection & ignition system. (N3/10)
I have found what I think are the correct circuit diagrams for your CLK 230K with engine 111.975, transmission 722.6. Complete with Legends for your information. Wire colours are given with German abbreviations, e.g., ge = yellow, rt = red, sw = black, ws = white.
Document PE07.61-p-2000NA covers engines with/without compressor with connectors 1 & 3. as of 1/6/2000.
Document PE07.61-p-2000NB covers engines with/without compressor with connectors 4 & 5, as of 2000. With CODE 440a - cruise control.
I can see no connector 2 for this engine.