Hi there, I am a newbie here on this forum so be easy with me !!

I have a 1999 Mazda B3000 Troy Lee Design. Problem I am having is the the ABS warning light ...what usually causes this to come on and how do I get it to go off. Also for some reason when it is on you can not communicate with the computer. Right now they will not pass the truck for an inspection sticker because they can not communicate with the computer. Any help or suggestions would be greatly appreciated !!
Thank You