I’m writing this to help out anyone here on this board wanting to hook up a sub and/or amp in a 2014 MKZ 2.0T. I found that there was some help on this forum, but not as much as I needed. I don't know anything about other models or years nor was I able to find the mystery white plastic piece designed to pull the power wire through the firewall. Hopefully this helps someone in my boat. I have pictures with comments but the way they uploaded are kind of out of order. Sorry, I got in a hurry.
So I'm not a mechanic or a audiophile but I have always liked having a decent sound system including a sub for some bass. I started off going to audio express and told the guy I didn’t want a pounding system nor did I want to drop $1000. His only offer was 2 JL w0 12’s and a 600w kenwood amp for $1200 installed. Fast forward to a few hours of research and I bought a Rockford P300 Punch powered 12” sub. The built in amp is 300w. Nothing fancy and I’m not even sure it was going to satisfy the bass I wanted. But it was $189 on Amazon. I bought a Rockford wiring kit and an Audio Control LC2i2 line out converter. All links below.
I got the line out converter because I didn’t want to replace the lcd nav entertainment system. I also didn’t want to have anything to do with taking apart the dash. It also solves the issue of a remote wire which is needed to shut off the amp when the care isn’t on to keep it from draining the battery. After finding out about the line out converter and that I wouldn’t have to do something special with the remote wire or take apart the dash, my only challenge really at this point was getting through the firewall.
I found out later that the person who owned the car before me had already done some wiring, but I couldn’t find where they got through the firewall. I thought about going through the main wiring harness but not only is that grommet super tight, its near impossible to get to from the firewall and not very accessible under the dash. I found that there was room in the grommet for the hood opener cable. I poked through with a phillips but ended up poking the grommet out and I have no idea where it is. I need to silicone that up but I’m thinking water isn’t getting up there anyway, but still a good idea to get it sealed up. I have a few pictures to show how I pulled the cable but basically, I just pushed a wire through from the inside and eventually saw the cable under the hood. I tied that wire to the power wire and pulled it through. Way easier than I thought.
Getting the power wire from there to the back was fairly easy. The door jam pulls up easily enough and you can work the wire to the back seat along the side of the car. Once at the back seat, the bottom of the seat has 2 latches and the whole damn seat comes out. Awesome. Immediate access to the trunk. The back rests come down easily giving access to the back as well; that comes in handy later when wiring the cables on the other side of the carpet.
To access the 6x9s, you have to take the panel off from the back plate up in the trunk. I recommend taking that off and not putting it back on until you’re completely certain you’re done. Those push pins are tough to get out. Maybe a better tool would work but I had a hell of a time. So, the line out converter basically takes amplified signal and turns it into unamplified signal which is what an amp will need so that it can amplify it. Simple enough. To do this, you have to hook into the speaker wire at the 6x9 from within the trunk. I found that someone had already done this and had speaker wires run to the side unused. I actually just ran some speaker wire to a random speaker I had in the house to confirm they were live. That saved me some time. I ran those wires to the line out converter.
The sub/amp combo actually came with a quick release connector for the power, remote, and ground. That made it much easier for me to wire up everything. I connected the main power wire to the same type of wire I used for the remote wire and ran that to the line out converter to supply it with power. I did the same for the ground wire. I then connected a remote wire from the “remote out” on the line out converter to the quick release connector in the remote wire position which was just between the power and ground position.
The ground wire actually was kind of an issue. My ground wire wasn’t very long, which is good, but it made it a bit difficult to find a good spot. I found one on the passenger side that I liked but it forced me to face the speaker forward towards the driver. Through reading and a tip from a friend, I found that its typically facing away from the driver but all the way up against the back seat. It should sound better that way. After fiddling with it, I found that was right. I eventually found three holes in the bottom of the trunk that I didn’t think much of at first. I came across some videos about grounding and found a ground option to screw three screws around the ground loop. I'm guessing thats where the previous owner had their amp grounded. So I used the same holes which made the option of me turning things around to test sounds much easier instead of picking a spot on either side.
I found that moving the carpet along the driver or passenger side is not necessarily difficult, but it moves it around and mine really didn’t get back in the right position leaving some gaps and its looser now etc. If I were to do it again, I would try to move these as little as possible.
I guess that’s it. The system sounds pretty good after tuning. It is as much as I needed. I think the previous owner left behind some upgraded front door speakers cuz they sound amazing. I lucked out there I think. I hope it helps someone else and provides the information you need. Feel free to ask questions.
Line out converter
Rockford Sub/Amp combo.