I have a 1999 MB C280 and my diags tell me that my "check engine" light is on because my o2 sensors are out. I've found a reputable place to buy the sensors, I just need to know where the sensors are located and how to replace them. I found a source to get an O2 wrench for this model Benz, but like I said - where are the sensors, and what is the process to replace them?

Thanks for the help!

 

They are located on the exhaust manifold, and after the cats as I remember. I think there are 4 or them. Someone please correct if I am wrong. How do you know all the O2 sensors are bad? I had a check engine lite and had to replace one sensor, the dealer did it, I never saw the OBD2 information.

Anyway that is the general area.

 

Thanks C280 Wizard. I have to check with the garage that did the diags to find out whihc sensor it is. As far as replacing goes - what would you rate the level of difficulty?

 

You will need a O2 socket specific for the O2 you buy, and it would be nice to have a lift, or your going to be on your back. Unhook the connector and screw out the bad one and screw in the new one and reconnect the wire.

 

somewhere sometime ago, i read that...O2 sensors should give a voltage reading between 0V and 1V, and that if OBD2 reader does not tell u which sensor is bad, you just use a multi meter and check which sensor gives a reading that is extreme to one side.

something like that....in principal. so correct me if i am wrong.

 

The main thing to remember is to make sure you do not touch the end of the new sensor with anything. Even your fingers!

 

No chemicals, like an anti-seize compound, on the threads either.

 

I just bought a Bosch O2 sensor, and the threads have, what looks like, anti-seize compound pre-applied to the threads.

 

There is "anti-seize compound", "RTV", etc.. that are designed to be O2 sensor "safe". That is what would be applied to the new sensor.

But I would still do as Lugnut said, keep all chemicals away if at all possible. Obviously if it came with it, it should be ok.

Hope this helps

 

Yeah, I'm talking about regular anti-seize or other chemicals. I was in a Z28 club several years ago and we rented a garage to do work on lifts. About a dozen guys replaced O2 sensors and put anti-seize on them because the exhaust systems were aluminum. EVERY O2 sensor died.