BMW M4 ABS Failure: Speed Sensors or Something Worse?

Hey there! I had some experience with a similar issue on my 2020 BMW M3 last summer (I have some experience working on cars but nothing too advanced). That ABS/traction control behavior sounds very familiar, my M3 was doing exactly the same thing, and it was super annoying! Took it to my regular workshop, and after running diagnostics, they found that the ABS control unit itself was faulty. Ended up costing me around 1000 Euro for the replacement and programming, but it fixed the issue completely. The symptoms disappeared right away, and the car's been running perfectly since then. Before you proceed though, could you tell me if you've noticed any other warning lights or unusual behavior? Also, have you had any recent work done on the braking system? These details would help narrow down if you're dealing with the same issue I had. I know BMWs can be tricky with these systems, but my M3 (and previously owned 3 Series) have been solid otherwise.

Just had my last service at 120,503 KM and experienced the exact same symptoms a few months ago! In my case, it turned out to be the wheel speed sensor, much cheaper fix than replacing the whole ABS unit. The mechanic mentioned they found dirt buildup around the sensor, cleaned it thoroughly, and still got error codes, so they replaced it. Total cost was around 300 including labor, and it solved both the ABS and traction control issues completely. Definitely worth checking the sensors first before jumping to bigger repairs. Now the car runs perfectly smooth again, typical M4 performance. Would suggest getting those sensors checked first, much more common issue than a full ABS unit failure in these newer models. If you're handy with basic diagnostics, you can even check the sensor connections yourself before heading to the shop.

Thanks for the update! Yeah, you're absolutely right about checking the wheel speed sensors first, wish I had done that before jumping straight to the ABS unit replacement. Would've saved me quite a bit of cash! Looking back at my M3's case, I probably should've been more thorough with the initial diagnosis. When I think about it now, the symptoms were pretty similar to a sensor issue. My mechanic might have been a bit quick to replace the whole unit without fully checking the sensors first. Did your mechanic mention which specific wheel sensor was causing the problem? In these BMWs, I've learned that the front sensors tend to get dirtier faster due to all the brake dust. Since my ABS unit replacement, I've been really careful about keeping those sensor areas clean during regular maintenance. Also, the fact that you fixed it for around 300 versus my 1000 for the whole unit... ouch! But hey, live and learn, right? At least both our cars are running smoothly now. Really appreciate you sharing your experience, might help other M owners save some serious money by checking those sensors first!

Thanks for the feedback! Actually, it was my front right sensor that was the culprit. You're spot on about the brake dust, my mechanic mentioned the same thing. Guess we all learn these things the hard way sometimes! Really sorry you had to go through the whole ABS unit replacement though, that's a painful hit to the wallet. I've started paying more attention to keeping those sensors clean during my regular maintenance routine now. Even got myself a proper sensor cleaning kit, definitely worth the investment. The M4 is such a brilliant car when everything's working properly, and these small maintenance details really make a difference. You live and learn with these performance cars, right? Next time you have any issues, definitely get them to check those sensors first. Thanks for the great discussion, it's always helpful chatting with other M owners who understand these quirks. Keep enjoying that M3!