an 04 focus No ABS?

Hello I have this focus that I replaced the driver side rear drum/bearing last week because the bearing was shot. To get the drum off I had to beat it slightly with a hammer. I replaced the bearing/drum and it sounds great. but now the ABS light has come on and the the ABS does not work. is there a sensor in the wheel area? Or is there other issues that i don't know about?
Thanks