You lower the rear of the exhaust & support it & use a special O2 sensor socket to remove the sensor.
With ODB2 on that car almost any scanner will bring up codes that should lead to a correct diagnosis.
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)