I know exactly what this is, it is called the ABS Tone ring, replaced 2 myself, not overly complicated, yet not overly simply. It is common in these Escapes mine is 2005. My abs and 4x4 light came on, and sure enough it was the tone ring, happened to the other side 6 months later. Look behind the tire for something that looks like an exposed gear, with teeth connected to the axel, it is likely broken. there is one on all 4 tires, in my experience the fronts are more likely to fail. I got them at 1aauto.com. Luckily i sprung for the 2 pack since it was only a little bit more. Turns out my logic/intuition was correct, if one failed the other probably will, 6 months later bam! good luck.