Used to alert you that the brake pads are wearing down
This sensor is like a wear alarm on your brake pads. When the pads on your brake system wear down, the pad sensors may alert you of their condition. When the brake pad wears down, the brake pad wear sensor is also worn down and may eventually trigger the warning light to alert you. Once the warning light is triggered, the wear sensor needs to be replaced.
These sensors should be replaced each time you replace your pads.