Does anybody have problem with 1996 Mercedes Benz S500, fail

Does anybody have problem with 1996 Mercedes Benz S500, failed smog test caused by OBD and passed Emission?
I have a 1996 Mercedes Benz failed smong test caused by OBD On Board Diagnostic and passed emission. We replaced the O2 sensor and still failed, no failure codes detected when plugged to the OBD2 handheld device. Does anybody ever experienced this problem? help.

don't take this as gospel. A friend of mine had the same car. Did the same thing. after some number of visits to the dealership they called in a factory tech from New Jersey. looks there was some sort of corrosion on the terminals of one of the computers and when that has been cleaned the car performed properly. Something about low voltage because by resistance of the corrosion.

Have a dealer check all the service bulletins for this problem that's where the factory tech got the fix

At least this is what my friend told me.

The OBD monitors most likely haven't run.