the mastercylinder has a low fluid sensor in it. if the brake fluid gets below it it will turn the light on . just put a little brake fluid in the mastercylinder and put the top back on crank it up and see if the light goes out. if it is still on put a little more in . you just don't want to fill it up because when you have to push the caliper back to put new pads on when it gets time to do it then you will have room in the mastercylinder to hold it .so just put enough brake fluid in the master cylinder to make the light go out. mine took only 1/4 inch of fluid and when i did my pads the fluid was up at the cap.so i figured if the engineer would have put the low fluid sensor 1/4 inch lower he would have sequenized it with the pad change[oh well] so just put 1/4 " in the master cylinder.........light should go out.
