I have discovered the source of an annoying rattle/cracking sound. It's the panel behind the passenger seat and vertical to the parcel shelf. I can't figure out how to remove it though. I am thinking about adding some of that sound deadener from another post to the panels when I remove and refit them. Anybody taken these out before?

 

If it is panel in front of the battery. You need to remove the parcel shelf and remove the screws that hold the aluminum bar. Then they will pull forward. Not a lot of room in there for sound deadening if I remember. Look up YouTube video on replacing battery.

 

The panel is ABOVE the battery, the backing panels above the parcel shelf. The battery was relatively easy to get to when I swapped it out. Getting out out is another matter...The rattle is in the higher up panel behind and above the parcel shelf. Knocking on it sounds hollow.