If it says brake circuit failure, and your brakes work fine and you think that none of the lights are out, then check the wiring harness in the trunk. It's easy, just open your trunk lid and on the left nahd side look where the wires come from the car and up into the trunk lid. Check that they are in good shape and line up well.
I had a brake light circuit fauilure OBC message all the time, but my brake lights worked fine, turns out some of the wires had been bent back and forth enough times that they broke. This can cause all sorts of electrical havoc too. It's worth a look, there are plenty of DIY to fix this problem too.
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