Light does not stay on all the time.
My ABS light is coming on. Brakes seem to be okay. on 1998 Mazda B2500
You probably have an abs sensor ring with a crack in it. Rust forms on the ends of the half-shafts and causes these to crack and need to be replaced. When the crack is not spreading the ring too far you can get an intermittant signal.
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To diagnose properly need a trouble code. Unfortunately you can't go to a parts house to get that code/codes.