That's it... you're missing the backup parking assistance sensors. I bet that is the pre-wiring for that installation. My factory installed parking assist is to the right of the 400/100you don't have the back up beeping thing ? the third on from the left on the bottom row turns my backup sensors on and off.
I just found this too. I don't have the reverse sensors, or the subwoofer, or factory fog lights. So I figured it's one of those but I don't know which one. Anyone know?I have a 2010 FJ which I thought had all the options but I found a blank switch on the center console lower row which is prewired. Any ideas on the function?