PowerStop® - Electronic Pad Wear Sensor

Modern car manufacturers have added a very convenient feature to their instrument panels: a brake pad wear indicator that lights up when the pads are due for replacement. This sensor isn't particularly sophisticated; it's just a wire, and sometimes a resistor, that is worn away as the pads wear down. When the wire is worn through and breaks the circuit, the light is turned on, letting you know the pads are worn. Needless to say, to get that light to stay out when you replace the pads, the sensor has to be replaced too!

Okay, it's a little more complicated than that: some higher-end cars have a wire that wears through at about 50% pad wear. The onboard computer then looks at the mileage since the pads were replaced, and estimates how much pad life remains and displays that for your perusal in the Driver Information Center on the instrument panel. The pad wear sensor also has a resistor inside that maintains continuity across the sensor circuit, although no longer as a direct short like before the wire wears away. When the resistor eventually wears away, leaving the circuit completely open, the mileage displayed goes to nearly nothing. That resistor generally is finished at about 25% pad thickness remaining. You may need to use a factory scan tool (read: Go To The Dealer) to reset the whole system after replacing the pads and sensors. Otherwise, you'll constantly get either a worn pad indication or an error message.

Bottom line: once the sensor is worn down far enough, there's no way to avoid replacing it to keep from getting either a warning that your pads are nearly gone, or an out-and-out error message. Well, there's one way: you could simply replace the brake pads before they reach that 50% wear: we sell brake pads and sensors, so we don't care!