Wiring HU to reverse wire

I'm trying to run the reverse gear wire on the back of the HU to the reverse wire so the HU will switch into camera mode when I put it into reverse.

But I can't figure out why it's not working... I tried splicing the HU wire into the reverse wire and that didn't work. I also tried applying a charge directly from the HU to the battery and that didn't work either.

What am I doing wrong? It's an App Radio 2 (SPH-DA100)

 

I wasn't sure what year truck you had so I checked it on a 2007 but the wire you are looking for is in the drivers kick panel and is +trigger red/white wire in a grey 12 pin plug and should be pin #1. Make sure you meter the wire first because i am not responsible if you mess something up but it should come on with the reverse light which in turn should activate the back up cam wire on your had unit.

To test the wire have a multi meter set to DC ground the black lead and put the red lead on the wire you are testing. Put your truck in reverse (don't start the truck just turn the ignition on) and you should get 12v when in reverse. If this is the case you have the correct wire, tap into it and enjoy your back up cam.

I hope this helps in your endeavor. Also if you have a different year model than the one I looked up let me know and I will get you the proper color and harness it should be basically the same for all the second gen stuff.

 

Also this goes without saying but just in case if you are on any sort of incline when putting the truck in gear it will roll so apply the park break as a fail safe just in case.

 

http://www.tacomaworld.com/forum/audio-video/30889-oem-camera-connection-below-dash.html

see post #6 on this thread. Hope it helps.