change tires now ABS INOP

my abs inop light is on after changing my rear tires, and the light wasnt on before . what can it be and what are theeffects of having that abs inop light on?:confused:

Are the tires the same size as the front? Was any of the wiring or connectors for the rear ABS disturbed during the process? Do you have traction control?

Check you wiring and plugins