my TC went full stupid unrideable (till you toggle TC to off - then 100% normal to ride but of course without any traction control)
good main dealer replaced front sensor, updated bikes i-level and gave the bike back
less than 500 yards later I went back same issue - they worked on the bike with technical for hours scratching their heads - in the end their explanation as to the wrong diagnosis first round was due to the way ASC operates - its far more sensitive to the data stream from the wheel speed sensors than ABS is
ABS doesn't have a clue if intermittent weird data is each wheel under slippery condition doing different things to each other - or a faulty sensor
ASC is seeking parity from both sensors all the time - and if it sees ANY difference (passed x threshold) it cuts the power
If the info is intermittent madness from fracturing ABS sensor wires (as is the BMW way), ASC gets a headache as it can't determine which wheel is causing the wild difference its seeing - so for safety throws a fault from the list of codes it has - in that unusual circumstance it always starts with the first in the list - thus claims the front is dead - when 9 out of 10 times its always the rear that has actually failed
that failure aligns exactly with mates bike - his did this for 2 years - two dealerships and five visits and a new front sensor - in the end he found out which was wrong (rear) by reversing which sensor was connected to which input
