A bit 'windy' but before I installed a 3rd party LCD mirror on my 09 tacoma I read many threads on the subject. And while I couldn't find a direct pin-out description for my factory mirror harness/connector; By putting together some info from one post to another, was able to complete the job rather easily.
I guess the 09's were part complete in that the truck came with the LCD tailgate camera with harness installed, but no LCD mirror. Even today if you want to just plug in the factory or OEM rear view LCD mirror with a direct interface harness, that mirror assembly will still cost you $700+ from Toyota.
So for me, the 'tailgatecamera' LCD mirror (4.5" display) for ~$150 would have to do. The first thing I found was that the 4 conductor cable from the tailgate camera to the overhead above the stock mirror was spliced somewhere? That was the only tricky part in the install.
Removing the overhead light/compartment panel reveals a 14 pin rectangular connector with 7 conductors. Rather than try and match color with function from previous posts, all I did was use a VOM and find Ground, VCC (Accessory 12V+) and 12V+ when in REVERSE. For my 09 those conductors were as follows:
1. VCC 12V+ = Solid Green conductor
2. GND = White with Black Stripe
3. 12V Reverse = Solid RED conductor
The above is all that is required to activate the Mirror power and Video display.
Last are the (4) conductors to/from the tailgate camera. These conductors provide 12V power to camera and bring camera Video to the Mirror. Caution, if you look at the wire colors at the tailgate connector, they may not be the same as those in the overhead 14 pin connector (least wise in my case).
So from previous posts, I figured what might be 12V power to the camera and the Video output from the camera. those conductors were:
1. Camera 12V+ = Black
2. Camera 12V gnd = (shield) wire
3. Video + = Red with Grey band
4. Video - = White with Grey band.
Hooking up is easy. Cut the 14 pin connector off the overhead harness and prepare (strip) each wire for splicing.
The 'tailgatecamera' unit harness comes with (2) RCA video jacks, and 3 wires labeled 12V ACC, Ground, and Reverse Signal. These 3 wires get connected to the OEM overhead harness wires:
VCC 12V+ = Solid Green conductor
GND = White with Black Stripe
12V Reverse = Solid RED conductor
You also need to splice the camera 12V and Ground to the above.
When this is complete, test by turning the key to ACC and noting the green light on the mirror.
Now all you have left is hooking up the Video signal from the camera to mirror harness. And here you have a choice? You can either cut the RCA jack off and splice the center conductor to the Video + wire and the shield to the Video - wire. Or add a RCA (male) jack to the Video + and - leads (from the tailgate harness) and just plug that into the mirror RCA 'camera' jack.
There is plenty of room in the overhead between the headliner and the roof on either side of the light compartment to place the extra cable from the Mirror assembly.
My suggestion, draw it all out with wires defined, get a decent VOM and jumper wires with clips so you can test everything before making final splices. I purchased a decent VOM, strippers, crimpers butt splices and jumper wires from harbor freight for less than $40. Good luck and if you can find a OEM LCD mirror with a direct harness plug in, that's great! Unfortunetely, I couldn't and didn't have the extra $$ to spend at Toyota