abs light

ok so my abs light has been on for awhile now and i want to fix it (it gets annoying) so my dad knows a guy at his work who has an abs code scaner so we borrowed it. hooked it up tonight and chose my blazer and tried to read the codes and it came up with "No Data at ALDL" have no idea what that means so just wondering if anyone can help me out w/ that or w/ my abs light being on. thanks!

does your ABS work?
 
you could check for dirty ABS sensors, and disconected or broken wires to  start
hope this helps

aight thanks i'll check it out not today tho lotta snow and cold out lol