I have a 2006 FX4. I now have the OEM tray with the aux input jack. I saw on a friend's 2008 that there is an additional wiring harness coming off the main harness with the plug that plugs into the bottom of the OEM tray plug. I'm guessing it just goes into the main harness and those wires somehow end up in the connector on the back of the HU.

I have a non-audiophile HU - 6 disc changer with the factory Sirius (which I do not ever plan on using).

I just want to figure out how to connect the line in tray to the HU so I can use it as a line in.

Has anyone figured out how to do this without buying a PIE? Surely there is some way to either make or buy a separate connector that plugs directly into the bottom of the tray's plug and then to the back of the radio (unplugging the Sirius radio from the radio is fine since I'll never use it anyway).