2013 ML350 Bluetec, 375 000 km (about 233 000 miles). Had a check engine light for the bank 1 sensor 1 oxygen sensor. I replaced the sensor and so far so good for 2 days. The check engine light reappeared this morning with the code P2195. Not the same code as before, but it's still related to the bank 1 sensor 1 oxygen sensor. I wonder if anyone else had a problem like this? Could a vacuum or exhaust leak cause this code?

The suv seems to run fine, except for the fuel economy that took a hit.

 

Repeat DTC fault with new Lambda installed...

Do you happen to have the old sensor on hand ?

Check old sensor for oil contamination inside the harness connector.

"Stuck-Lean" fault is not fuel pump related because bank2 reports fine.
This is a MAP engine, not MAF vac. leak.

> Do you pretty much trust your new sensor part:
part number match and supplier trusted?


BTW after this is all settled out you'll need to replace bank2 upstream also to keep engine balanced - (Don't bother Downstreams sensors).

 

Thanks for the reply! I just noticed it. The replacement O2 sensor was a cheap brand from China that I got from Amazon for 50$. You might be correct that the culprit could be the sensor itself if it comes from a cheap brand.

I ordered a quality Bosch O2 sensor, made in Germany.

https://www.fcpeuro.com/products/mer...sch-0065421718

I'll install it this week and I'll update this thread if the code comes back. I'll return the cheap one from Amazon (hopefully I can).

 

Is this a hard job? Any links on YouTube on how to replace this?

 

I didn't have time to do it. I dropped the SUV off to my local indy shop. They said it was easily accessible. Bank 1 sensor 1 means it should be located on the right side (passenger side in North America), before the catalytic converter. Not sure if it's easier to get to from the top of the engine or the bottom. Maybe someone else can chime in.

By the way, the check engine light hasn't returned since the new Bosch oxygen sensor was installed. So far so good...

 

Good to read your success with reliable lambda!
Now Bk2 needs the exact same thing ASAP so both banks remain identical.

 

Should it be changed now or wait for a check engine light?

 

Now is the answer, dont wait for total failure.

You will notice your engine response improving over the next 500Miles

 

Well well well... the check engine light reappeared this morning. I scanned it and got P0030, which is still related to the bank 1 sensor 1 oxygen sensor. The oxygen sensor is a brand new Bosch upstream sensor (17200).

What is going on here? Wiring damage? I'll take a look at it this weekend. The suv runs fine and fuel mileage seems the same. No apparent symptoms other than the CEL. Could the ECM be the culprit?

 

Is Bank1 still stuck lean and Bk2 all good - So fuel is fine.
It's time to compare the harness values at ECU or all the eay at exhaust harness connector.


M276 lambda pinout sample
Looks like the +12V power source is shared ie. ok!
The GND side is switched by the ECU to manage the heater current.

Use an oscilloscope to see +12V square pulses.

50/50 chance something wiring is going to turn up...
No colateral codes from a good MB scanner?
then compare Bk1 vs.2 live data.

 

Thank you! Regarding your diagram, it is for the M276. I have the OM642. Is it similar to the M276?

 

Good chances pinout is not compatible but circuit is similar where:

• The +12V side is sharing fuse.
• The current is controlled by ECU on the GND side with a pulse to GND.

Compare both banks live values.

> Different point of view....
-- I'm getting the sense Lambda is flagging something wrong with the engine -
-- We've been assuming "Bad sensor" where sensor may really be measuring something true about the engine.

 

Problem solved!

It turned out to be a leak in the silver/grey pipe on the right of the turbo. The pipe has 2 gaskets, a green one where it connects near the turbo on top and a black one that goes on the other end at the bottom. The person who worked on my car before (I know excatly which shop!) added silicone instead of using the green gasket... resulting in a leak and oil spewing everywhere in the back of the engine, near where the EGR valve is. This caused the B1S1 O2 sensor to be out of whack and throw the code. While I was in there changing the gaskets, I noticed an oil leak near the back of the engine, near the turbo. My PCV valve was shot and I replaced it. I suppose it was 13 years old and had 380 000 km. I think it was the original one. I plan on inspecting it very often. I'll probably change it every 100 000 km as a maintenance/precaution item.

So if you ever get a B1S1 oxygen sensor code, check the gaskets in the pipe around the turbo first! My original sensor was probably still good... but I replaced it with a new quality Bosch sensor... oh well.

Btw, I'm not a mechanic expert, but it seems the OM642 doesn't have a Bank 2 Sensor 1? My scanner tool only shows one sensor pre cat. Is it possible the OM642 only uses one before the catalytic converter? Maybe a pro or a MB tech can chime in? Based on my visual inspection, I don't see another one...

 

V6 two banks: 1 passenger & 2 driver
Upstream pre-cat: S1
Downstream post-cat: S2

You're saying your OM642 has no downstreams sensors: B1/2-S2

 

Correct. Pardon the confusion. I'm basically asking if there's only one sensor pre cat (upstream as you mentioned) and one sensor post cat (downstream). Most other engines that I know (gas engines) use 2 pre cat and 2 post cat.