Pioneer AVIC-8500NEX wiring questions

I recently purchased a Pioneer AVIC-8500NEX head unit for my '07 Shelby GT. I purchased the wiring harness from Crutchfield, and have figured out all of the wiring, save for one wire marked "Reverse Gear Signal Input". I've watched a bunch of videos on wiring up a backup camera in the car, and want to do that, but all of them basically show tapping into the backup light wiring in the trunk for power for the camera and also grounding it in the trunk, and then running the video cable for the camera up to the head unit. None of them mention anything about this reverse gear signal input wire. Where do I need to run this to connect it properly? Any help would be greatly appreciated. Thanks!

the reverse signal wire from stereo ties into the red wire that's on the rca end plugged into head unit (if you want to). Like this.



I just added a reverse camera to my pioneer dmh-1500nex and I didn't tie that wire into the head unit. I just plugged the rca cable into HU and all wiring was tapped into at the rear of the car. When the reverse lights get power, it powers the camera on and displays on HU.

I did attach the wire to the HU on my truck though, so I believe you can wire it either way and it will work.

I found it easier to tap into the reverse light at the housing. I would have had to disassemble the shifter housing to access the reverse wiring.