Quote Originally Posted by CKTofu View Post
Which 12V circuit in the trunk of the car that is closed whenever the car is on? I imagine one of the lights in the back is constantly on, but I don't know which at the moment.

I'm at the start of the same process, I have a rear view camera and a Pioneer head unit that I'm installing in my '09 Aveo, so this thread's already been a help to me.
Well actually the circuit is not closed when not in reverse it is open but it is switched fom ground, I confirmed it with my multimeter using the car chassis as ground I saw the the positive wire had a constant +12 volt in it.

But your statement had me think I should check the other light and see if it's the same, I instinctively connected on the driver's side backup light because the wire harness of the trunk lid goes there, so maybe the switch is in the middle of the circuit and on the passenger side there is no constant +12 volt on the positive I'll test it out this evening.