I went to emmisions and failed because I had no.

I went to emmisions and failed because I had no voltage at the data link connector, also my check engiene light, I thought it was because I had a blown fuse ( cigg lighter) so I went to get new fuse for it and it worked once then was immedicately blown after one use. I also tried to reset the check engiene light, which I discoonected the battery for 20 mins, recconected it and it still stayed on. I need help, what do you think?