Hi,
Did this start after refueling or adding DEF (diesel exhaust fluid)? I attached the info related to the codes you provided. They indicate the vehicle is producing excessive NOx gasses. NOx is Nitrogen oxide which is created when nitrogen and oxygen combust under pressure and at a high temp. They are poisonous and are controlled by the vehicle.
Selective Catalytic Reduction (SCR) is the most common method in diesel vehicle exhausts to lower NOx gasses. DEF is added to vehicles with Selective Catalyst Reduction (SCR) like yours to reduce the NOx output to nearly 0.
I hope that made sense, and I hope you understand why I asked if this started after refueling or adding DEF.
If you look at the attachments, it explains what is happening and what needs to be done. I highlighted the section which includes the diagnostics.
Take a look through these and let me know if you have questions. Also, note that the code 207F was rewritten by BMW to be 4D17 (manufacturer code and not a "P" code). You will note that the two, 4D17 and P20EE are identified in the attached info.
One last thought, make sure the engine is running at a normal operating temperature. If it is running hotter than normal, that can cause this to happen as well.
Let me know if you have questions.
Take care,
Joe
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Wednesday, August 18th, 2021 AT 9:52 PM