How do you reset O2 sensor light on 1986 MB 560 sl?

Answer 1

Getting free info on this will be difficult, standard car computer systems interfaces didnt get standardized until the 90s, but I have worked with onboard ECU's and would make the guess that if you have replaced the 02 sensor, as they do go bad, the default way to reset this is to disconnect the battery power for a minute or so, disclaimer: only someone trained in how to service battery connections should attempt this using proper tools and eye protection. Before the hood of any car is even opened, the person looking at the engine should wear safety goggles. That being said, in most ECU's when the power is reset there will be a training phase where the ECU learns how the engine is performing and adjusts itself. So repowering the ECU then driving for a while may clear the light.

MB is different, they will go far beyond what standard vehicles do, so there could be a specific reset switch or maybe its a fuse that has to be pulled for a few seconds, or it could be that a MB adjustment must be performed to dial in the new 02 sensor where the custom electronic tester must connect to and calibrate this in the ECU.

02 sensors are very sensitive, too rich of a mixture could quickly wear them out; never spray or add anything to clean the engine or injectors unless you make sure with MB that its safe, using the wrong kind of "injector cleaner" could ruin your $150 02 sensor in seconds