I agree with the above, you need attention on your brakes. To take it one step further, there are two brake lining sensors, one on the front and one on the rear (one side only for each axle). The light doesn't tell you whether it is the front or the back that is worn out, so you need to check both.

If you need pads, you will receive recommendations to change the rotors at the same time. I would do so, and did on my 2003 X5 3.0, but others will try and get a second life out of the rotors. BMW does not recommend turning them on a lathe.

Since the warning light came on, you need a new brake lining sensor (front or rear, possibly both). The sensors are single-use items.

You can go to a dealer, which is somewhat expensive. You can go to an independent mechanic, and have them use either OEM BMW parts, or jobber parts. Many like the Axxis Deluxe pads, for similar performance to the OEM pads without the dust. I used them and would do so again.

If you want to do the repair yourself, there is a DIY article on the X5World home page. If you haven't done similar work before, you may want to have someone work with you who has done it before. It isn't particularly complicated, and no harder than doing brakes on many other vehicles, but brakes are a safety item and deserve respect.

Hope that helps. Welcome to X5World.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue