How do you replace oxygen sensor in a Mercedes Benz c280?

Answer 1

I just did this job two weeks ago on a 1995 C280 so I can give you the rundown.

Aside from normal hand tools and safety equipment you'll need:

A 22mm metric obstruction wrench. This is kind of a C shaped box end wrench. HF sells a set for about $12. A flex head 22mm box end would probably also work.

A hydraulic jack and two jack stands. A chunk of 2x4 would also help.

The Bosch Exact Fit O2 sensors. I used the Bosch universal but in this application I'd go with the exact fit parts next time. Space is limited especially on the front sensor and I'd pay the extra $30 or so for the made to fit part as a time saver. The splice kit with the universal looks good but takes a fair amount of time also so again I'd opt for the exact fit.

Here is the procedure:

Jack up the right side of the car and secure on jack stands. Make sure you'll have enough room to slide well under the car, at least to where the drive shaft is over your chest.

Next remove the two bolts that hold the exhaust to the transmission and set them aside.

Now move to the rear of the car and remove the two rubber hangers from the muffler by hand or with a pry bar. Once you have these two hangers off you should support the muffler with the jack and move back to the center of the car to remove the middle rubber hanger.

Once the exhaust is free slowly lower it down until you have access to the two sensors. The front one required me to drop the system nearly all the way to the ground.

Here is where the C shaped box end wrench comes in handy. I don't know what those engineers were thinking but its impossible to get a normal wrench or socket on these sensors without dropping the pipes out of the car! Sure you've for the right replacement parts? Good, now cut the wires within and inch or two of where they come out of the sensor on the OLD parts obviously.

Next slip the obstruction wrench over the sensor and give it a smack with the heel of your hand or a hammer to jar the sensor loose. Once you've broken it loose it should turn out by hand. Repeat this on the other sensor, connect the wires and reinstall the exhaust hangers and you're done!

I have a pretty well stocked tool box and this was the only way I found to do it with the exhaust still in the car. An o2 sensor socket WILL NOT FIT on these due to space limitations under the car.

--Previous answer below--

Its actually pretty easy.

My new one came attached to a bit of the air in take ducting. I matched the piece under the hood, loosened the clamps securing that part of the ducting, (think I may have had to do another part to get some leeway too) - old out, new in. Electrical wires snap off and on. Took maybe 10 mins.

TO ABOVE POSTER ^

I don't think you have the slightest clue between a MAF sensor and an o2 sensor. Under the hood? We are talking about a sensor (o2) that is located before and after the catalytic converter UNDER THE CAR on the exhaust pipes......nothing to do with anything under the hood. A MAF connects to the intake ducting and air filter ducting. Meters air intake and compensates fuel trim accordingly. The o2 sensor measures the exhaust gas ONLY to determine that the car is running the proper AFR (air fuel ratios) and thus allows the ECU to compensate more or less fuel when needed. The o2 sensors after the cat are purely for evaluating the effectivness of the catalytic coverter, makign sure it releasing fumes within emission standards. Just thought I'd clear that one up. The very top poster is 100% correct about replacing the o2's. Follow his insight.