My ABS light is on and I've changed the fuse and relay where is the sensor at. Can someone take a pic of its location for me. My truck I thought was only rear ABS but it has a the relay for 4 wheel how can I tell if its 2 or 4 wheel ABS here is a pic of my master cylinder I thought that 4 wheel ABS had a plug on it. Ohh and my rear wheels lock up so there is something wrong just dont know what to do next. My rear end is 7.5 if that matters where the sensor is.