I have had the abs light on for a few weeks and today when I went to stop the pedal was so hard that with all my strength I could not budge the pedal at all. I had to use emergency brake to stop. after that it worked fine for a while but did two more times right after that. I drove to Ford dealership and rest of the way it worked fine. Dealership replaced the rear sensor and master cylinder sensor. pedal is ok now but ABS light came back on again. I'm now scared issue will happen again and dealer says the ABS module may need to be replaced. I can't keep paying for "Might work" issues. Any thoughts? 1999 F-150 5.4l 4X4