Your abs light stays on all the time on your 2000 Ford F-150 pick-up?

Answer 1

Quick background: ABS system uses a toothed ring (looks like a gear) on the back side of the rotor and a magnetic sensor that detects the "teeth" going by. This is how the car knows if the wheel locked up. If the sensor is malfunctioning, or the ring is missing (did you replace rotors with non-abs rotor) the system will throw a fault light. If the teeth are full of dirt that has a high metal content, the sensor will become confused and not detect motion and you will get the abs light.