Number 5 40a fuse blows everytime I put the key in start position.

What is your question?

Had a fuse (num 5 sbf 40a) go out a week ago, changed it and I was good. After I drove 130 miles to my job site and was ready to go home, the same fuse blows when I try to start the car. I walk over to Walmart, grab another fuse, and throw it in and think that I'll be able to find out what's wrong when I get home. Wrong, it blows the new fuse and when I did an odb2 test there's no codes (although the I/M had more red X's than checks). I towed it all the way home. Now I have no idea how to work on electrical issues, because I'm used to working on cars with carbs (this car is the only modern car I own). I'd like to fix it myself but don't know how to diagnose it.

What makes this problem better or worse?

No idea

How long has your 2010 Subaru Outback had this problem?

A few weeks