I have a 2001 Excursion with a 5.4. It feels like a front brake rotor is warped, but I have replaced all 4 rotors, pads and calipers. I have also had the front rotors turned 2 times. This problem came about 2 yrs ago when a steel plate fell off of a flatbed trailer and went under my vehicle while travelling on the interstate. No obvious damage was done. I have had to 2 shops 2 times plus time I have spent on it. No one seems to be able to figure out the problem . Would it be a problem with an abs sensor ? How can I tell ? Thanks , Robby