Typically the sensors for low pads are not on every wheel. Uneven pad ware can see metal on metal before the sensor has gone off (has happened to me on my 330ci where pieces of metal were coming off my disk but the sensor had not yet come on!)
It has a complicated warning system of lasers, photon accelerators and pixie dust, allowing the car to rear end the car in front or vanishing through hedges when applying the brakes. When this happens, get them replaced.
It has a complicated warning system of lasers, photon accelerators and pixie dust, allowing the car to rear end the car in front or vanishing through hedges when applying the brakes. When this happens, get them replaced.