Hello, I have been dealing with a check engine light for over 2 years stemming from a faulty O2 sensor. Long story short changed the 4 sensors and full pipe catalytic converters and still light is on. They tell me one is running rich and the other opposite, but no one seems to know where the problem stems from to fix it. I hope someone can give me some guidance. Thank you.

 

Try this https://www.ebay.com/itm/Car-CEL-Fix...temCondition=3

 

There are different styles/types of Oxygen sensors; most are Zirconia, some are Titania and they are not interchangeable.
I would start be being absolutely certain you are using the correct MB sensor.

 

Thank you so much for taking the time to help.
RMP

 

Did you change the sensors or a shop ?
what brand, plug and play or universal wire in ?

 

I purchased what was said to be OMC from Rockauto and a shop installed them. They have been swapped out at least twice each, still nothing.

 

I also buy parts from Rockauto but, that really doesn't clarify the correct sensor issue. Assuming they are okay and working fine as intended, you may solve the issue by replacing the spark plugs. These cars are 15 years old and even without a lot of mileage it may be best to change plugs and wires. Also if a non sensor safe RTV was used to seal something in the past like a leaking valve cover it could effect the oxygen sensor. I hope you have the car in an independent owned garage that specializes in european/mercedes vehicles. They will have the proper scan tool to dig deep into the Mercedes engine codes. Good Luck!