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I tried searching this forum but couldn't find anything related. I have a GLK250 Bluetec, and it has the urea delete kit (don't remember how it's called).
Sometimes, randomly but mostly going uphill, I will feel the transmission downshift one gear and the engine revs go up. It will still display the Drive symbol but I can't change gears manually anymore. It stores a code and on next engine startup it illuminates the CEL. P0234 (overboost condition) is what it shows. However, the car doesn't seem to be missing power and to be in a limp mode (except for the trans switching mode). If I clear the code the car will behave normally again for a while.
I'm not sure how to proceed for the diagnostic. I tried logging the manifold pressure in Torque and it gives weird results. Each time that the boost goes over 20psi, it will display 0 until it comes back down to 15 again. Does anyone has the same issue with Torque ? Otherwise I don't feel any loss of power so I suppose that not a true reading and maybe not related to my issue, but this makes it impossibile to see if it overboosts or not.
There is a vacuum line going to the turbocharger for the internal waste gate. Check and make sure the arm moves freely and that you don't have a vacuum leak. You can see the arm and where the line attaches in this photo...
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P0234 overboost
