I figured out it’s bolted behind the trunk fuse panel.Might I suggest you look in your owners manual? Looks like the rear fuse box for a V2. From the 2011 owners manual:
Rear Compartment Fuse
Block (CTS-V Coupe and
Sedan)
The rear compartment fuse block is
located on top of the battery, on the
right side of the trunk. The battery
access door must be removed to
access the fuse block.
The vehicle may not be equipped
with all of the fuses, relays, and
features shown.