does your tech have diagnostic equipment that has the capability to read faults from the BMW abs system?
in that case the abs/dsc control module has most likely failed. This is very common.
replacing it with a new one is hugely expensive, so I would consider sending it out for repair to BBA Reman (easily found on google).
Sorry if you were hoping for a different answer, please don't shoot the messenger - I can only give the honest answer, which I have. Please remember that a low rating PUNISHES me for my honest and prompt response, and I receive nothing for my time and answer until a positive rating is clicked.Please let me know if you have further questions. Please do not forget to click a positive rating as this is the only way I receive credit for my answer, thank you. Best wishes with your vehicle.