I have to replace this thing but when I crawled under there this morning, I could only find two allen head bolts that hold the charcoal canister on. I tried to remove those but all they do is turn, they won't loosen (or tighten for that matter). It looks like the leak diagnosis pump is attached to the charcoal canister bracket but I'll be darned if I can get it off.

 

It's common for those two screws to just turn, what is happening the nut is just turning in the plastic. You need to feel around on the pump and you'll find some screws mounting it to the bracket, then you can remove it by itself. Otherwise cut the plastic and replace it when you put it back together.

 

Could you post up a pic of that pump? Curious, if that's what was causing the "chirping sound" from the rear passenger seat area?

 

The same thing has happened to me. I'm going to have to cut it out. I've went ahead and ordered a new charcoal canister to replace it, too. It looks like I got the wrong part, though.