As I understand it the sensor is simply a wire. There is no intelligence in the sensor. First stage when the rotor wears away at the sensor until it touches the wire you will get a break pad warning. Second stage when the rotor wears through the wire completely you get a brake pad critical warning. I have over the years reused unworn sensors with success. Possibly one needs to remove and reconnect the sensor for a reset?

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2013 X5 3.5i M Sport
2004 M3 cabriolet SMG