I opened up the rear access panel to take a look at the fuse box (Passenger side interior trim panel--made of a carpet covered fiberboard material...). Pulled it off with a distinctive snap. Now I can't figure out how to put the panel back. The pins line up with the holes, but they don't snap into place. Nothing looks broken. There's also this random plastic tray that doesn't seem to go anywhere. Wtf.

I can't find an exploded diagram for the life of me.

 

Are talking about the piece that covers the battery? If so, there is a black plastic piece at the top that slides back and forth (front to back of car) that has to align with the grooves on the cover. It’s kind of a pain, but you have to put the cover up with that piece all the way to the rear. Then get the covered positioned and slide the plastic piece forward to lock it in place.

if you heard a snap, you may have broken one of these tabs, and the cover isn’t catching the plastic slide.

 

Spare terminal for positive
In this pic, the plastic piece I’m talking about is at the top right. It’s kind of hard to see because it blends in with the fuse box. There is another tab connected that is on the other side (left in this pic). Both tabs are connected on one piece of plastic.

Battery housing
Kind of easier to see here. The piece is directly below the beige tabs where the holes align with the inserts on the cover.

Hope this helps!

 

H'okay, that was helpful. Thanks. The slidey black plastic piece came off with cover. Nothing looks broken, just gotta figure out where that black plastic piece fits in the housing.

 

Got it all figured out. The slidey black plastic piece has two slots that fit onto two tabs that allow the piece to slide back and forth (front/rear of the vehicle). Piece slides forward to lock, backwards to unlock. The piece can be moved with the cover in place by using a screwdriver inserted into the air "vents" on the underside of the plastic storage cubby. There's an interface there if you just take a flashlight and look from underneath.