So I have a 2005 F150 Scab and I purchased a new Pioneer AVH-5600BHS. I purchased all the iPhone cables for the app radio features and a back up camera as well. On to my issue. I have spent hours researching trying to find what wire I need to tap into for the reverse trigger/signal for the head unit. I have read that it is black w/ pink stripe, green w/yellow, green w/ violet and many more. I am accessing the wires in the door sill area on the drivers side. I got a multimeter and tested numerous wires for power when it is switched in reverse. I cannot find it. I just need to know which wire I need to use and the best spot to access it. Any advise?