Reverse sense wire....where is it?

[serug]

okay, I fixed the issue. turns out, for some reason I can't understand, that when the car is on, started and/or in acc., there is a constant +12v on the positive line for the backup lights. even when the car is not in reverse. when you put it in reverse, the voltage drops to ~11.23. funny thing is that the negative line also has a constant +12v even when the car is not in reverse, but when you do put it into reverse the negative line voltage drops to ~1v. so, I just connected the sense wire to the negative and set the HU to sense a GND instead of BATTERY. Thank you guys for the help. thumbs up to AveoJunk. I appreciate it!