E-Class (W212) 2010 - 2016: E 350, E 550
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Error code appear 0745 & 0749

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Old May 13, 2026 | 04:50 AM
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W212 and W124
Error code appear 0745 & 0749

Hi everyone,

I had an issues on my Vehicle W212 E300 M272 Engine with the error code in details below:
  • 0745: Mixture too lean bank 1
  • 0749: Mixture too lean bank 2
I already replaced both downstream O2 sensor since the value is not balanced between each other, attached the value before replaced:


After replacing both sensor, the value is balanced but the check engine returned with the same issues and error codes.

Also I already replaced the breather hose with part number A2720181382.

The vehicle doesn't show the weird symptoms the idle is smooth not rough, however the idle feels more shaky during the cold start and it feels maybe around 30 seconds and the rough idle is gone when the idle going down into 600-700rpm.

Need your advice and guide.

Thank you all
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Old May 13, 2026 | 03:15 PM
  #2  
TimC300's Avatar
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From: MA Coast
W204 2010 C300 4matic Sport M272
First thing i'd do is remove the air filter box and inspect all the gaskets. the one at the elbow to throttle body, maf to elbow, air box seal. I replaced my air box seal because it looked worn, after replacing it the box fit on tighter and the metal clip snapped on over the top much better where before it felt loose.





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Old May 13, 2026 | 03:28 PM
  #3  
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W212 MY'14 M276-3.5NA @75kMi
lean banks mixtures

Originally Posted by redzkisuk
Hi everyone,

I had an issues on my Vehicle W212 E300 M272 Engine with the error code in details below:
  • 0745: Mixture too lean bank 1
  • 0749: Mixture too lean bank 2
I already replaced both downstream O2 sensor since the value is not balanced between each other, attached the value before replaced:


After replacing both sensor, the value is balanced but the check engine returned with the same issues and error codes.

Also I already replaced the breather hose with part number A2720181382.

The vehicle doesn't show the weird symptoms the idle is smooth not rough, however the idle feels more shaky during the cold start and it feels maybe around 30 seconds and the rough idle is gone when the idle going down into 600-700rpm.

Need your advice and guide.

Thank you all
I don't know who guessed downstream sensors as a solution for this.... UPSTREAM perhaps but not without diagnosis first.

You have two lean banks faults... read the fuel pressure under load: stable or low??
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