This is for a 2010, but the 2009 should be the same or very close:
You need something to convert the 12 VDC of your truck to 6 VDC and you need a shielded cable with an RCA plug on one end.
Below and to the left of the steering wheel, there is a little hinged compartment. Open it fully, then pull it upwards and towards the rear of the truck to remove it. Now, you can see a fusebox.
(photo borrowed from a post by DNahas: http://www.tacomaworld.com/forum/aud...elow-dash.html
At the upper left of the fusebox, there should be two white plug/socket assemblies. Unplug the lower one (Factory Camera connector). It should have four wires connected to it.
The wires are:
Black: +6 Volts DC supply to camera (connect to your 6 VDC source)
White: Camera video output shield (connect to the shield of your RCA plug cable)
Red: Camera video output (connect to the center of your RCA plug cable)
Taped: 6 VDC ground (connect to your 6 VDC source)
Your video quality will be better if you leave the Factory Camera connector unplugged. Be sure that you make your connections to the wires on the right side, not the socket on the left which is attached to the fusebox.
Now, look at the white plug/socket assembly at the upper left of the fusebox, above the Factory Camera connector. It's numbered like this, looking at it from the right side:
Pin 7 should have a red wire. Connect that red wire to the backup light input of your HU and the 12 VDC input of your 6 VDC source. Some trucks have another red wire, or a pink wire, on the same plug. Be sure that you connect to the right wire. The right wire should be at + 12 VDC when your backup lights are on, and 0 VDC when they are off.
Be sure to go into the menu of your HU and turn on the backup camera.
A couple of notes:
1. DNahas connected his video shield to the taped wire instead of the white wire. If I had been in his position, I would have done the same thing. That's the way it normally would be wired, but Toyota didn't do it the normal way. He was working without the electrical wiring diagram, so he didn't know. It worked, but the video quality will be better if you use the white wire.
2. I've read elsewhere on this forum that the backup light wire on the upper plug is pink, not red. Maybe it is on other trucks, but on the 2010, the backup light wire on pin 7 is red.