When you look down into the hole where the sensor goes you see the slotted disc. I imagine I spray cleaner and turn the wheel to get it cleaned. You show the front disc. Why does the code say rear. In all the years I've owned this X it's never coded a front wheel. I 'll clean both, but are those sensors interchangeable from front to back visa versa?
BTW, yesterday, I backed up until the light went out, 30 feet. Than drove round and round the parking lot, 100 feet , lights stayed out, overjoyed when the ABS kicked in on the rain soaked pavement. Headed out the drive about 100 yrds. down the road and bingo; lights back on.

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X5 3.0 AUTO -2001 - 238,000 miles