C204 2011 Exhaust Back Pressure & Boost Pressure Sensor


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Aug 23, 2021
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Your Mercedes
C Class 220CDI (s204)
I just wanted to add to this thread as it's one that comes up if you Google P047128, same symptoms as above over a number of weeks. Eventually engine light came on and ODB recorded code P0471 - you can reset this with a standard ODB reader, but to drill down more you need something like the iCarsoft MB v2.0 to read / reset codes directly from ECU.

I replaced the back pressure sensor but continued to experience the same issues, although the engine light didn't come on the car would drop power and the ECU recorded P047128. Watching the sensor readings on the MB v2.0 the back pressure would report 1 bar then occasionally jump to 2 bar, even at idle, until ignition was cycled. I suspected an electrical issue and decided to take the car to an indie MB specialist for diagnostics, they plugged in their star system and told me the mix of MAF, temp and back pressure sensors were out of calibration and this was corrected. What this involved I don't know but long story short this seems to have sorted the issue having covered 500 miles with no issues when previously I couldn't get past 5 so I'm hopeful. Sensor now reads a steady 1.15 bar at idle instead of jumping around.

If anything changes I'll update the thread but otherwise I hope this helps somebody.
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