“When BMW connect their PC on the car they quickly search if the car is modified.
If they see the DTC code related to a software modification you directly loose the warranty.
To not show this dtc you’ve two ways.
First, you can delete the DTC directly in the software (search 8209 in 16bits in the DTC area).
Or, better, you can correct the CVN to have the same CVN like the original car.
This second way is better because in Germany (for example) the CVN is checked by the MOT and or by the TUV.
If the CVN is the same as the original for the related VIN, they think that the car is not tuned.
But concerning the warranty is more complicated. If the ECU is not open, if the CVN is corrected don’t think that BMW is completely flowed. It exists FASTA. Behind this bmw name, there is a logging system what records all the interesting parameters like : rpm / torque / boost pressure ect.. If they have a doubt concerning the fact the car is original, they will look at this.
One advice. If something wrong with the car, put the car back to original first and if the car can ride, make some kilometers, FASTA will record orignal data and you can pray to keep the warranty.”