Now you see it…..
Now you don’t!!
First off If your not willing to fit yourself into your trunk, you may wish to rethink this DYI.
All in all this was a fairly simple DIY. You will have to seal the Fin location on the trunk deck, but if you're painting rally stripes on this can be down at that time. This is not meant to be the "last word" on final location, but it worked for me and XM/ONstar work just fine. There are some steps that are not step by step, but if you cannot figure it out you shouldn’t attempt or can PM me. So......
After exposing the trunk by removing all plastic retainers you will remove Fin by removing 1 bolt and unclipping the plugs. The fin will need to be removed from the actual antenna by removing 4 #8 torx screws.
Carefully remove these two antenna wires from the main wire harness. Once you get back by the taillights there is another rolex connecter to unplug leaving about a 2 foot section of the antenna disconnected. You will use this later in the rear seat area to connect to the XM/Onstar antenna.
Continue removing the two wires and re-taping the wire harness until you reach the top of the wheel well, or even with the back of the trunk as shown below 2 pics. There is a gray foam block here for reference and a nice place to zip tie the onstar/xm cables in place. I covered the cables with a plastic wire protector as seen in the pics.
The antenna cables will ultimately be tucked in behind the trunk liners as shown by the yellow lines. The Circle with X will be where the cable passes into the rear seat area.
You will first need to remove the side and rear plastic trim pieces. These are just clipped in and gentle prying will remove. NOTE: The rear trim piece is made up of two pieces molded together. Make sure you get under the main honey comb piece shown in later pics.
The yellow circle below is where the antenna will ultimately be located.
Now release the rear seat cushion. This is done by placing a screwdriver in the respective holes on each side and giving a firm “pop”. The seat will fold down.
You will remove the two plastic retainers (only 1 shown) so you can fold back the rubber insulation. This allows access to grab the antenna wires from the trunk.
At this point you will need to fabricate some form of mounting bracket. I utilized a 50 cent flat iron from Menard’s and bent it as shown. It is approximately 1 ½ inch from the top of the bracket to top of antenna. This allow for it to fit under the rear plastic trim shown later.
You will also need to drill in the bracket indicated by the yellow circle below. You will also need to measure and mark holes in the metal rear deck frame and drill holes for the mounting bracket. I utilized 2 small flat head bolts and nuts with locktite. Plug in the 2 foot antenna removed from the trunk into the end that you passed through from the trunk into the rear seat area, and then plug into the antenna when needed.
The last step you will need to do is cut out some of the honey-comb plastic on the rear trim piece so it will lay over top of the onstar antenna without hitting it.
All you have to do now is reassemble 1. Rubber mat. 2. Rear Seat. 3. Side trims 4. Rear trim.
My XM radio worked fine and onstar operator was able to locate my exact position. For fun, I actually covered the Antenna with a metal bucket, and still had reception.