How To: Fit aftermarket Reverse Sensors

[Tonto]

its the yellow wire that needs to be attached to 12v. I tried that yesterday with the rear 12v socket (I believe its 12v, might need confirming) and it made no difference, if i connect the red to battery it will be on constantly.. red to reverse light, black = ground and yellow only if car has canbus (if sio it will need connected to a 12v wire). So unless the rear passenger socket isnt 12v then maybe thats why it didnt work, do you know where i could pick up a 12v wire easily enough from?