my abs light comes on when I start driving forward and never turns off except for when I turn off the car. I took off both front wheels and cleaned off the magnetic contacts inside the wheel hub, I also took off the black abs cover and unplugged the relay and then plugged it back in (battery was disconnected when I did everything) but no change. Is it possible I need a new relay? and if so, could I get one that its from autozone or radioshack or is it benz specific?

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1990 190E 3.0L