2000 GMC Yukon Break issue
 

I’m having a problem with my front breaks I have replaced rotors, calipers, pads, and a bad break line, The breaks work great until you get close to stopping sometimes not everytime they will start to make a noise that you can feel in the pedal like it’s pulsing and it will grab hard when it does this. What I’m wondering is could it be a break censor or is it something like the ABS unit. This was happening before I replaced anything.
Any help would be appreciated