I think you may have solved my problem as well. I have the EXACT same problem with my 2002 focus. I will go to autozone tomorrow to see if i get the same code as you but i did just hear a hiss just like you described tonite. How hard was this hose to replace? What tools and how long did it take you? Instructions somewhere. I am not too car savy but i have a technical mind and can normally figure stuff out with a little help. please let me know as this problem is really starting to aggrivate me! Also what is the technical name for the hose?