Replacing Brake Pads on an E90 - Warning
A word of advice for DIYers. When you replace the pads on an E90 you should also replace the sensors whether they are worn thru or not. I recently did all four wheels on my 66k mile E90, I had 6mm left on the pads. I wanted to replace the pads to get rid of the black dust from the BMW pads.
I bought a set of premium ceramics from David Zechausen, these new pads fit and worked beautifully. I had no "brake" warning lights before the install or after the install.
Then after a few days of driving, I decided to reset the miles on the CBS computer - thats when I got an alarm telling me that the brake pads were worn and needed replacement. After many attempts to reset, and the advice of a friendly BMW tech, I replaced both original but "good" sensors with new ones and VOILA the brake light and warning went away. It seems that the sensors on the E90 are different from those on older BMWs and they have two sets of wear elements, the first element wears down to tell the computer that the pad is half worn and the second element tells the computer that the pad is toast. The first element won't set off a brake alarm UNLESS you try to reset the CBS mileage.
If you are replacing pads on a very low mileage car you can probably skip the sensor replacement but it is a good idea
to measure the resistance of the sensor at its plug - anything over 1 ohm of resistance could trigger a CBS brake light