my 95 E420 gave me these codes
 

Car started to make noise when cold and hesitates. I ran the codes and here is what i got:

02 O2S --> LH1-SFI
20 Speed Signal --> EA

can you help identify what is ailing it?

Thanks, Joe

Please elaborate on the "noise" with as much detail as possible.

Is this an ASR car?

My 93 400E is throwing codes all the time because the harness is bad. I clear them and then they appear again about 6 weeks later. Sometimes I get different ones.
Regards, Eric

The noise sounds like a high pitch whistle that seems to come from the front side when the engine is running. I am thinking it is the belt... When I rev it up the noise goes away and come back when in idle. Not sure if one of the components that runs by the belt is going bad. Also during early morning starts the car shakes and hesitates and sometimes it turns off. Last year the car failed 1st emissions inspection but then passed a second time around after I replaced the plugs... I ordered an O2 sensor that I intend to replace next week and also plan to have the belt replaced as well. Hopefully these will help. Any other ideas?

The only thing I would add to my first post is the smog pump. It only runs when the engine is cold. It's the only thing that only runs when the engine is cold, but that doesn't account for your other symptoms.

Does this car have ASR? Has the engine wire harness ever been replaced? What about the spark plug wires?

yes...is the code conistant? reproducible I mean?