I completed this mod today. Took me an hour tops, its actually easier than changing headlight bulbs.
Stole the info from
this thread
This
post in particular
Repeating most of it here, with a few changes based on my experience.
I replaced my shark fin antenna with a flat Camry one.
I have a 2011 4runner Trail KDSS with NAV & JBL
Over time the XM reception just kept getting worse. Driving near anything of any height at all and it cuts out. Could be due to the gobi rack I have surrounding it, but this is my first try at a fix. If it doesn't work I will try something else.(more elevation above the roof rack??)
Based on the threads above, I sucked it up and ordered part number 86960-33010-CO. This is the Camry antenna, color matched to my black 4runner.
(CO=Black)
It fits perfectly, except the plug, keep reading.
I installed it after receiving it. It works. (Not sure how good yet, but time will tell. I'll update this thread after I drive a few miles)
2/20/2020 UPDATE: I Had a 55 mile trip today, parts of this route include underpasses, tall trees and more various spots where I always lose reception, including at a stop light with a 2 story building and bunch of power lines next to the road. I'm happy to report this works perfectly now!! I didn't lose the signal all day in any of those spots like in the past.
This is a 100% fix for reception issues.
Steps:
1) Pull the rubber hatch seal up about 3-4 inches, just slightly off the body.
2) Gently pull the headliner down a few inches and the 3 clips in the next step will pop down.
3) Remove the three headliner clips along top rear of headliner near tail gate.
4) Gently drop down the headliner, being careful not to crease headliner.
5) Unclip satellite antenna now exposed beneath the headliner. (squeeze and pull apart)
6) Use a 22mm wrench to loosen and remove nut holding shark fin to truck roof. (It's barely even tight)
7) Lift out the unattached shark fin from top of roof (from the outside).
8) Mine had blue square connector. Replacement flat Camry antenna has very similar gray square connector, but not a perfect match. See photo. That tiny difference prevents you from being able to connect the Camry antenna to the 4runner wire. So just swap the connectors.
9) Swap connectors. Very easy to do. Gently pry up white plastic piece from top, removing completely. Then slide tiny flathead screwdriver into square face from the front and lift the little clip up to release the wire. With the clip lifted, slide the wire out of it. It took a bit of fiddling to get it to slide loose.
10) Follow same procedure and reverse it to move blue square connector to the new replacement flat Camry antenna.
11) Install on roof by threading through and tightening 22mm threaded hex nut up against roof.
12) Insert blue square connector into wire beneath headliner.
13) Gently push headliner back into place and snap the clips back in
I did not crease my headliner, or take out any additional trim pieces.
Borrowed photos below as well as some of my own.