I have an 03 F150 supercrew FX4 and I noticed today that my ABS light has came on and won't go off. I know I need to replace the front pads and rotors, but what will cause the light to come on?

 

A fault in the ABS system will turn on the ABS light.

Check the rear differential sensor, it's the most common failure.

 

the light can come on if any of the sensors have a fault in them. a bad enough wheel bearing can cause an ABS light. a problem with the module itself. if you have a scanner that reads ABS codes look at the codes and see what wheel it says that way you can at least have a starting point.