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Check engine lights throw codes. I’ve rarely seen ANY cars with “no codes” check engine light or not. I suspect his code reader can’t read BMW codes properly.
 

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3100 boost pressure deactivation is not a 1/2 code. It’s set and stored like any other code. 3100 however is not the causal fault but a symptom of another problem which will set a separate code.
 

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@plus1111
30FF is underboost. It means your wastegates are failing or your not supplying proper vacuum to the actuators. Simple diagnosis here honestly. Measure vacuum directly at your wastegates and you should see around 15hg. If you have proper vacuum then your wastegates are worn and your turbos are shot. This is usually apparent with a wastegate rattle on deceleration and also seems to show up mostly when it’s hot outside and air mass is lower compared to cool dense air. If you would like to confirm this then you need to remove your cats and pump your wastegate actuators to 15hg and try and rotate the wastegate sealing doors. If you can turn them then they are too loose. Also you can look at the wastegate seats and see if the sealing doors are sitting flush against the turbo housings. On an 08 535 with 30FF I’d probably wager a small bet your turbos are failing.
If your vacuum is too low you could have collapsed vacuum lines, failed EPDWs or a vacuum leak.
3100 is boost pressure deactivation which is consequential of many other drivetrain codes including the 30FF.
 
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