The "check abs sensor" warning came up for about a week, and after that has not been back for a few months, or since. When I press on the brake pedal, brakes are working but strong repetitive thud is coming from both rear wheels. Feels like a thud that would come from a normally engaged abs system, yet slow and very loose, and on every time pressure is applied. Also when the vehicle is going over bumps, something seems to be very loose in the same area.When stopping, the thud seems to have a slight pull towards more resistance.