If you had a failed sensor or a failure in any part of the ABS system, it would give a code and the ABS light would be on until it was fixed, no if and or buts about that.

Are the service brakes in good condition? Fluid full, clean? Pads/rotors have enough meat on them? I have replaced frozen calipers on older trucks/Jeeps, not totally uncommon. The pulsing you feel could be a warped rotor from overheating. Maybe check the rotor surfaces to see if one is glazed or rusted on one side or looks chewed up in some way. You didn't mention any pulling to one side so that's probably not likely but doesn't cost anything to look. If you're feeling adventurous, maybe get a helper to press the brake pedal while you crack a bleeder or two to see if the fluid gushes out.

If the hydraulic side of the brakes check out, you might ultimately need to have a scan tool put on it. It's an '02 which would be a DRB III. I don't remember what functionality there is (if any) to monitor the brake system on those trucks so I can't say exactly what someone might do but it might help to pinpoint something.