easy, remove the old brake sensor (its brittle plastic, not rubber) and cut the wire off the dead sensor and splice it ito the new sensor. it doesnt matter how you wire it up. no + or - wires.

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I swear, my cars are like a girlfriend.
Sometimes its a rough ride, sometimes its smooth motorin'.
Sometimes she doesnt like how i treat her and sometimes i dont like how she behaves.
BUT at the end of the day, she loves it when I am inside her.

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'91 850i
'05 X5 4.4i
'09 Clubman S