have 2001 GMC, ABS light came on, didn't think much about it, $hit happens, but when i turned the truck of, the brake pressure modulator valve under the driver's door on inside of frame was still humming, sounded like my cheap holley blue, just not quite as loud, couldn't figure out how to shut it off so i pulled the 60amp ABS fuse, is it starving for fluid or has it just gone bad? resivoire was full of fluid btw