Trouble clearing brake warning

[jnetter]

After about 54k miles, my front pads were ready for replacement. It's an easy DIY job to do the pads and wear sensor, but I can't seem to clear the warning message. I tried it using the display button method and with BimmerLink. Either way, it fails. Has anyone had success with this? Any input is appreciated.

 

[jadnashuanh]

If the indicator lamp came on, I'm pretty sure you have to replace the wear sensor in addition to the brake pads. The wear sensor, depending on the type, gets literally worn down as the brakes approach the end of their life, and opens a circuit that is detected by the computer. The only way to make it go out is to replace the sensor, as the diagnostics will still be reading that open (worn through) sensor input.
https://www.newtis.info/tisv2/a/en/i01-i3-94-hat/components-connectors/components/components-with-b/b105-brake-pad-wear-sensor-front-left/X1948on

 

[jnetter]

Thanks for the reply. I did replace the wear sensor when I did the pads. I'm wondering how the sensor works. I figured the sensor grounded to the rotor when the plastic wore off and closed a circuit, but that's just a guess. But the connector for the sensor has two conductors, so I'm not really sure...

 

[jadnashuanh]

The page I linked to implies BMW uses two different types of sensors depending on maybe market or options. They are not interchangeable. I do not know what would happen if you had the wrong type, or if the connector is even the same. One has a resistor in it and gives a two-stage warning, the other does not. In one, it breaks the loop, in the other, there are two loops, and you get a different warning as each one is successively broken.

 

[jnetter]

Sorry - I should have looked at your link. Basically, at new condition, there should be 0 ohms between the two pins. At 6mm of wear, there should be ~470 ohms. At 4mm, it should be open. So I likely either have a bad sensor or a bad connection. The sensor itself appears sealed, but it's easy enough to check with an ohmmeter at the connector. Thanks - this gives me a place to look.

 

[Rowan]

I realize this is an old thread, but I figured I'd share my findings in case someone has the same issue. I was having the same problem resetting the brake service light after replacing the brake and sensors. Found out that you need to disengage the parking brake before attempting the reset. Hope this helps.

 

[fozza]

Thank you so much for this post. You just saved my day!
I have seen instructions on how to reset this warning after brake service, and none have mentioned to release the handbrake.
Again thanks for posting!