Just finished installing a couple of 12" subs under the rear seats a couple days ago and wanted to make a quick guide here in case anyone else is looking to do something similar. I wasn't really able to find any information on amp installation for these trucks since they're so new so I just basically figured it out as I went, but thankfully I can say that this is probably the easiest vehicle I've installed an amp on, and I've done it on quite a few, including a '17 and a '13 F150. This is the easiest. Crazy, but it's true. It's easier because there's only a couple of dash pieces to pull out to access all the wiring you need. No need to pull off the trim around the steering wheel, the center console, or any of that. No need to take out the screen either. Awesome.

This particular guide is for the 7-speaker base system. Not sure how either of the B&O systems are different. Feel free to add your findings here and I'll link to them.

This guide is for my preferred method of installing an amp, using a . I like this method because not only does it convert the signal to RCAs, but it also provides remote turn-on to the amp based and it comes with a remote **** to adjust the signal to the amp. Doing it this way also prevents any issues with the start/stop system on these trucks, because as long as the line output converter is receiving 12v and a speaker signal, the amp will stay powered on and the subs will keep hitting whether the engine is on or off. Works great every time.

So first step is to install the line output converter. To do that you'll need to splice into the factory speaker wiring. This is easily accessed by first pulling out the rubber mat on the top of the dash


And then using some trim removal tools pop out the clips holding on the dash speaker grill



Once that's off remove the (4) 7mm bolts holding on the dash speaker and the center dash trim piece.



Disconnect and remove the dash speaker and then use your trim removal tool to remove the large trim piece covering the system amp, starting at the front on the top and working your way back.




Now you'll have access to the wiring harness you'll want to tap into to install the line output converter. That was easy, right? To top it all off there's PLENTY of space in here for the converter, so no need to worry about stuffing everything behind the screen or a trim piece.



Unplug the two connectors in the back of the stock amplifier, one gray and one black. In the below photo I've already connected the line output converter, but you can still see the plugs. Just pinch the top tab down on them and they should pull out with a little wiggle action. The black one is the one we'll be tapping into. Go ahead and cut a little bit of the tape around the harness and peel it back to reveal the wire colors.



Now attach the line output converter according to the instructions that came with it, connecting its wires to the corresponding F150 system wires. My favorite way to splice into any automotive wiring is by using wire tap connectors . A HUGE thanks to @hotrod_renegade who got me the wiring diagram for this system. The colors you'll need are below:


Connect your RCA cable, your remote turn-on cable, and if applicable your remote bass **** cable, and run them together down off of the left of the amp. You should be able to get them down into the driver's footwell by reaching through the hole in the trim for the steering wheel. It helps if you put the steering wheel up all the way and you can even pop off the top of the trim surrounding the steering wheel. Once all your wires are down there, mount your bass **** using either adhesive or screws. Next we'll wire the power cable for the amp, then run them down the driver's side of the car together with the RCA and remote turn-on cables to behind the rear driver's side seat where we'll mount the amp.

If you look in the driver's footwell you should see a grommet to the left of the brake pedal with a zip-tie around the connection between the grommet and a factory wiring harness. If you snip that zip tie you should be able to open up that grommet a little and fit your power cable through just fine. I used a healthy and thicc 4 AWG wire, so anything smaller than that should fit just fine. I hooked the power cable to a metal clothes hanger and pushed it through the grommet from inside the cab through the firewall and into the engine bay.




Run it however you think looks best to the battery and install your fuse. Disconnect the negative battery terminal of the truck to avoid any short-circuiting or other electrical issues, then connect the power wire to the positive battery terminal. I ran my wire along the air intake.



Nice! All the tricky stuff is done! Now it's all easy. Now just run your power wire, your remote turn-on, and your RCAs under the trim on the driver's side. Pop off the door plate, then pull back the weather stripping on the entire lower half of the driver's side doors, both front and rear. With the weather stripping pulled back it should be pretty easy to get your wires all the way from the front to the back of the truck.



Behind the rear driver's seat I was able to pretty easily fit my hand between the rear fabric and the trim to reach and grab the cables to pull them that last little way. Once your wires are all run it's time to install the amp!



Connect everything you've run to your amp. For your amp's ground, luckily if you pull pack the top of the rear liner by the seat latch you'll see a factory ground location. Go ahead and just run your ground there!



To secure the amp back there all I did was just poke some holes in the rear liner and then zip-tie the amp to it. Pretty easy!

BOOM! Give yourself a pat on the back, your amp's all installed! Go ahead and run your wires to your subs and you're good to go!

 

Thanks man!! I’m clearing out the garage and hoping to do my install by summer!

 

This is all very similar to my 2011 install... save for the head unit access. Having the B&O 18-speaker, mine will be different, but the meat of this should work for all 2021's. Much appreciated!

 

Excellent write up, glad I could help! Did it look like there would be enough room behind the factory ACM for say, a Kicker Key amp? I don't have my truck yet but I'm thinking about running that amp with a nice component set up front.

 

Can't say for absolutely sure, but my initial instinct is that a Kicker Key would fit back there pretty easily. It's probably the most room I've ever seen behind a factory system, there's quite a bit of space back there. The shape of the space is a little awkward, but the space itself is pretty ample.

 

Nice write up, pictures of completed install.

 

I used my B&O subwoofer signal for my 10” subwoofer, the bass sounds cleaner, I tried using the rear speakers signal but I didnt like the sound

 

You are doing the lord's work!

 

A couple questions. Tomorrow i'm going to start mine. i'm putting a 5 channel in so it'll be a little different. i'll need all the door speaker wires to my line out converter.

1) i'll be installing a Lc6I , so do you have the full wiring diagram that shows front and rear speaker colors?

2) are they all on the BLACK connector behind the screen ?

3) i'll be doing the wiring a little different as well and i'm wondering if it will all fit down the driver side. i'll run 9 wire from the connector to the lc6i mounted behind the back seat, then 9 wire back to the existing wires i cut behind the screen. plus the amp power wire obviously. Will it all fit below the door sill on one side or will i have to run some down the passenger side?

4) did you replace the weather stripping ?

 

1. Rear speaker wire colors are LR+ White & green, LR- Brown & Yellow. RR+ Brown & White, RR- Brown and blue

2. Yes, all on the black connector

3. Probably depends on the gauge of speaker wire you’re using, but there’s a decent amount of space under there. It’s super easy to just pop the door sill off and look.

4. Nope. But be careful with it so you don’t bend any of the metal inside it too much.