The 1991 cars with ASR don't have ANY code memory or retrieval ability at all.
You will need to find a dealer that has a break-out box for that system to diagnose your problem.
Most likely is the throttle potentiometer at the back of the intake manifold.
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)