enjoimorenow

Hi all, new member here, and new Mercedes owner. I noticed that when i would drive over speed bumps or through dips there was a loud ping noise (like a metal spring snapping almost) from under the car. I jacked it up and there are two metal flanges hanging in the center of the car. I'm almost certain these are what are making the noises, but I'm just not sure what they are for or where they go. Is there a piece or cover that I am missing? I took a few pics to hopefully help.





I also have another question. I left my house today and check engine came on. Ran to Auto Zone to have them pull the codes. The codes were:

P0141-Heated Oxygen Sensor Bank 1 Sensor 2
P0420-Catalyst system efficiency below threshold bank 1
P0600-Serial communication link

I'm assuming these are all related codes due to a faulty oxygen sensor or possibly a bad connection (been driving around in a lot of snow this past week). Guess I just want to make sure those codes are right because for some reason the employee ran them as OEM Volkswagen. Also just wondering where the oxygen sensors are located, and how hard they are to replace. Are they all the same sensor or are there different ones (pre and post cat)?? And if they are different could someone give me the part number for Bank 1 Sensor 2?

Thanks for any help and Merry Christmas!!!!

samaritrey

you are missing a cover as well as what is that oil from?

Glyn M Ruck

Something that I can't make out is bent or broken. This is what it should look like. Same gearbox on a V6 - you will have one exhaust pipe. See downstream O2 sensor after Cat.



Your downstream O2 sensor has failed. Replace it & pray your Cat has not failed as well. You will only know once you have replaced or checked that it is still connected. Sensor 2 is the sensor on the exhaust after the Cat.

If the downstream sensor has failed you had better replace the upstream one as well.

enjoimorenow

well i'm doubting that the cat has failed. I just got emissions done on it on Thursday to get my plates and it passed. When I left the emissions place there were warnings that the Stability Control and Brake Assist weren't working but they went away after about 5 minutes. I parked the car last night and then this morning the check engine light was on.

It seems the downstream O2 sensor is the more expensive one. How essential is this to change? Should I not be driving the car until I replace it or can I wait until the weather warms up a little and do it. I was planning on doing an oil and brake change after the new year but I guess I might have to do it sooner.

Thanks.

Looking online i found it pretty cheap, but is it the 3-wire or 4-wire sensor? I'm assuming that this would work???

http://www.autopartswarehouse.com/de...USOS-4000.html

Glyn M Ruck

Good news - then your Cat is OK. The downstream sensor just monitors the Cat effectiveness. You can leave it until convenient & put up with the code. I would check out that bent bracket?? that is hanging down. I think it is from a heat shield. Just make sure it was not a brake line support - I don't somehow think so but check that it does not compromise safety.

enjoimorenow

ya i will get a better look at it when i can jack the car up but it's just cold outside right now and snow all over the ground so I need to let it warm up a bit. I'll get some better pictures of those bent brackets when I get it jacked up in the air. I do notice that trying to bend them they instantly snap back into place (straight down how they are in the pics) obviously that's not their intended "place" or whatever but idk where they go so i just figured i would see if anyone on here had a better idea. Thanks for your help!

Just want to make sure this is the right sensor before i order...

http://www.autopartswarehouse.com/de...USOS-4000.html

boom132

Still haven't answered the question about the oil everywhere... that can't be good at all.

enjoimorenow

that's not oil it's just grime from snowy roads and a terrible job of focusing by the camera. If it was spraying that much oil I think I would have had to fill it up by now.

Carsy

Looks to me like a bracket which held the under cover plastic protector. Looking at the other side there is one in place that is not bent.

It is bent in the direction that it was torn off.

You certainly would have felt/heard it being pulled off.

This is probably how your O2 Censor was damaged.

You may have to take the bracket/ brackets off & straighten them in the vice.

Have a good look in case there is other damage taken place.

Its probably a good idea to find another undercover protector.

Good luck.

LILBENZ230

OP - I don't think that is the correct replacement part. Seems very cheap, also says "universal part" - we have lots of trouble with these "universal parts". They fit fine but the car won't take it and the code will persist. You need OEM (Bosch, I believe).

Glyn M Ruck

Yes - sorry - did not answer that question. Do not use universal sensors on these cars. Get genuine MB Bosch heated sensors from someone like RMeuropean.

enjoimorenow

Thanks, glad I didn't order it yet! I'll do a search for that user and see what he charges. In the mean time, would this one work. It says Bosch Heated, but it says it works for either the up or downstream sensor? Also says minor modification required??

http://www.autopartswarehouse.com/sk...gs+Best+Seller

Thanks again!!!

Glyn M Ruck

Here - These are what you need from RMeuropean.