Brake Warning Light On? Understanding Brake Sensors

A Brake Warning Light Can Indicate It’s Time To Replace Brakes


Brake pads can have a safety feature of electronic wear sensors. When the brake pads get worn beyond the minimum thickness, the sensor will trigger a warning light on your dashboard that it is time to replace the brakes. When replacing your brake pads, you should also replace your brake sensor if your vehicle has one.

The wear sensor triggers the dashboard brake warning light when the sensor element comes in contact with the brake rotor. When brakes are new, the sensor wire is positioned near the backing plate of the pad.

As the pad wears down to the sensor wire, the sensor wire touches the brake rotor and electrically triggers the brake warning light circuit.

By design, the sensor is a throw-away component; If the wear sensor has done its job, and tripped the warning light by touching the rotor, then the wire has been ground away by friction on the rotor. It has to be replaced.

Even if you’re doing a brake job before the sensor wire has come in contact with the rotor, the sensor may look okay, but the heat of the brakes has likely caused hardening of the wire insulation and corroded the inner wiring, increasing its electrical resistance.

Sensor wires are generally inexpensive, so it makes sense to replace these every time you do a brake job, even if the sensor looks okay.

When you replace a sensor wire, especially if the warning light has been tripped, be sure to follow the OE recommended repair procedure to reset the warning light.

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