2008 F150 "Line In" Wiring Question
 

I hope this is the correct discussion board.

I have a 2008 F150 with with the premium or audiophile package, I'm not sure how to tell. I don't think it will be relevant to my question.

I am building an interface for a bluetooth adapter. Basically, I will replace the 3.5mm "Line In" jack with this "thing" I am building. However, I want to connect it back to the factory connector.

I did some preliminary investigation last night checking for space, fit, and general applicability of the idea. I noted that the "Line In" jack has a connector with 4 wires. That surprised me, I was expecting 3.

Does anyone know the pinouts of the connector and also the plug? I expected a left, right and ground on the connector. I expected a tip, ring, and sleeve on the 3.5mm jack.

Wish I had taken a picture, but alas hindsight is 20/20