The fuel computer provides a great deal of info beside check engine info. There is a "live data" stream that can provide info on the imputs from all of the sensors, that is where I would start.
You would need a MB scanner as ODB2 would not provide that info.
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)