2004 Toyota Highlander | Stereo Wiring Diagram 2004 Toyota Highlander. October 6th, 2012 Posted in Toyota Highlander. 2004 Toyota Highlander Stereo Wiring Information. Radio Constant 12V+ Wire: Blue/Black Radio Ignition Switched 12V+ Wire: Gray The stereo wiring diagram listed above is provided “as is” without any kind of warranty. Trailer Wiring Harness Installation - 2004 Toyota Click to view3:48When not in use, you simply coil up the wire, lift the carpeting cover back off and stow it in the plastic tray again. And with that, that will conclude our installation of the Tow Ready T1 Vehicle Wiring Harness, with the four full flat Author: etrailerViews: 5 2004-2007 Toyota Highlander Vehicle Wiring Chart and Diagram Listed below is the vehicle specific wiring diagram for your car alarm, remote starter or keyless entry installation into your 2004-2007 Toyota Highlander. This information outlines the wires location, color and polarity to help you identify the proper connection spots in the vehicle.