Whenever I go out on a short run and stop at various places my parking brake light comes on. I can categorically say that I've never used the thing. When it's on the car coasts fine with no hint if the brakes catching. I turn the car off and the light disappears.
I changed out the rotors and pads about a year back and was careful with the parking brake cables. Oh, and when I use the parking brake it works fine.
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More than likely, your brake fluid level is low. Check the reservoir.