Hi guys, Im' from Moscow, this is my first post here on mbworld. I call in for your help as i can't find solution among our service society on our forums. I drive C230K sport sedan imported from California.

So I've got a problem with mixture, as a result I have heavy on fuel and errors 201C P0172 - rich fuel mixture. I've spent too much time muself and in services to find the reason and have alredy replaced all possible things which could cause the problem.
I prepared to this post and made huge service work in advance (stop oil leakage to the harness, cam shaft magnets replacement, first O2 sensor replacement on new one, air flow sendor replacement on original new one, checked all connections in intake for some kinds of air leaks, system of recycling crankcase gases replaced: houses, valves, vacuum houses of cat heating system replaced)

For your information catalisators deleted from the system and O2 sensor after catalisator turned off electronically.

So what i have as of today:

-Low voltage on first O2 sensor 1000 mV istead 1500 mV (means rich mixture)
-big fuel consumption especially on idle and low speeds in traffic jams especially.
-self adaptations on idle and partial loads in plus
-fuel pressure 3,75 stable on idle rev
-idle rev is stable 750 rpm +-5


So the most hard for understanding is unlogical behaviour of ECM. We have as given by O2 sensor data - rich mixture and at the same time we see that ECM (ECU) trying to rich misture more

I have conducted some experiment where i arranged air leak inside the system and got high voltage of O2 sensor, and arranged air leak out and got low voltage o2 senser


Below some screenshots form StarDiag and my ELM327 of current data






Did anybody faced with such behaviour? What else i should check in your opinion?


P.S. sorry for mistakes in text and big pictures is it possible to make spoilers for pictures here?

 

Have you solved your problem ?

 

Did u solve the problem? I meet the same one, code coming out p0172 p201-001

 

Firstly how did you delete the o2 sensors electronically?
Secondly if you have in fact switched off closed loop. Why are you bothering to read o2 sensor values?

 

Hi! A solution? I have a similar problem with the m271 engine. No power, a little jerk and a lot of consumption.

 

Seems a common problem, got it aswell. I think it might be the 12$ hose beneath the airbox, going to change it and see if it makes a difference. Doesn't look like it has any cracks or tears in it.

 

In the meantime, a solution has been found. The failure was with the second catalyst. He collapsed and clogged the exhaust.

 

Thanks buddy will check out the catalyst

 

I have exact same problem. Can someone confirm it was the catalyst?

 

Same problem, did u fix it? Can you help me with this

 

can you confrim it, wich is the second catalyst

 

these codes also appear to me. who solved the problem? I have all the vacuum lines in order! Thanks whoever answers

 

these codes also appear to me. who solved the problem? I have all the vacuum lines in order! Thanks whoever answers

 

Hi, did you sokve the problem, i have same issue. B1S1 O2 is at 1.0 volt, lamda is 0.88 and fuel trims are +10.

 

In my case (M271 engine), the problem comes from the EGR valve. This valve is passing, but not all the time. The passing only happens on long rides, so when doing a test, the valve is still okay. But on long trips, the EGR valve is passing, and as a result, air passes through the exhaust. This causes the oxygen in the exhaust gas to increase, and the upstream oxygen sensor voltage goes high. The mixture self-adaptation increases to inject more fuel, but in fact, the current mixture is already in a rich condition (because a part of the air is lost to the exhaust).

When the EGR is not passing (after starting for a short time), no more air passes to the exhaust, but the mixture self-adaptation means the mixture is still in a rich condition. The result is that the upstream oxygen sensor goes down to a low value (in my case, around 1V).

Solution:

1. Erase the fault code.
2. Disable the EGR valve: insert a blind nut into the hose connected to the EGR valve.
3. Conduct a long ride.

After that, if the engine returns to normal condition, then this post can help you. If not, it is another case

 

I’m going through similar issues with my c230k as well. I’m going to do what you said to see if that helps me. I’m having self adaptation codes that keep coming back and a p200a hotfilm mass airflow sensor code that keeps coming back even after i replaced it with a new one.