Help installing aftermarket sub and sub amp

I am hoping someone can help me on this. I have a custom sub box I made for my coupe and had the amp and everything installed but I removed it all and sold the coupe. Now I would like to install it into my sedan but I can't find the directions I used to figure out how to get RCA output to put into the amp or where to tap for the 12v trigger to turn the amp on.

Does anyone have wiring diagrams or details on what wires to tap to install a sub amp? Also I don't know what I need to connect the tap wires to the amp. In my coupe I used a Soundgate LOCX which does not appear to exist anymore.

Does the sedan have a stock headunit? Also the factory amp?

If you do, then yeah you're going to need a line output converter (like the Soundgate LOCX you had) in your case, and attach it wires going into the factory amp for the rear speakers. RCAs go from there to amp. trigger wires for both will need to be tapped to a switched wire (off white, why I remember that? dunno lol) in that same harness.

Wiring colors somewhere in here. Looks all weird now with the new forum layout.
https://www.e46fanatics.com/threads/...sticky.245914/

Yup OEM HK headunit. That looks like the thread I need but you are right the format is messed up, I'll have to read through it.

Yeah I skimmed through it and it's like post 12