Actually the basics to code retrieval are exactly the same for these impulse systems as the Volvo impulse systems. With Volvo the wire for grounding and the light were incorporated into the test system. With the MB one must fashion his own LED light and grounding cable. Once wired, it works just like the Volvo system.
The prewired button on your car allows this prewired system to check only the DM (diagnostic module). if you wish to view the HFM (engine management) or CC/ISC (throttle control) or AB (airbag), or AC one must pick the right hole and do the wiring such that a 2-3 second grounding activity will excite the code. Read one after another until the first code is repeated and then the codes are erased in similar fashion to Volvo with a 6-8 second grounding signal.
Bosch Master, ASE Master, L1
33 years MB technician