Directechs.com said it was also the yellow/white under the dash at the data link connector under the drivers dash. It should be the only wire this color. I don't know what the resting voltage is in the wire, but there is an easy way to test it. If you have a good voltage meter (fluke perferably) just set it to AC voltage and drive around. The faster you go, the more voltage it will read through on the meter.

The new AVIC should have a auto learning speed sense on it like the kenwood nav. When you hook it up it might act funny (like it says your going 100 mph when your going actually going 20mph.) If it does that just keep driving around. It should auto learn your speed sense pulse.