2005 GMC Truck

I think you should take your vehicle to a parts store and have them do a scan for any codes. If your ABS light isn't on, you don't have a problem with sensors or any other ABS part. I your brake pedal really goes to the floor, you have low disc pads in the front, out of adjustment rear drum brakes, air in the lines, or a bad master cylinder. Check all of these things out, and I'm sure you will locate the problem. Most parts stores will scan free of charge, because you might buy the parts from them. Good luck.