A buddy and I installed a Rockford Fosgate p300-12T subwoofer in my 2022 civic sport today --- I haven't found any info on installing a sub in a 22 civic, so I thought I would document the process here. We are not experts so use this guide at your own risk 
That said, the install turned out very clean and is completely reversible barring a small hole through a rubber grommet in the firewall.
Signal wires:
My sub has a built in amp that can tap Hi level inputs. I wanted to tap the front door speakers since those seem to provide the most bass (I could be wrong on this as I only used my ear as a reference). To find these wires, we popped the panel behind the head unit. It pops right off with a plastic trim lever. There is a wiring harness attached to some sensor? on the trim panel that we disconnected so we could fully remove the panel.
![Image]()
After removing the panel, here is a photo looking down at the backside of the head unit. The bottom wiring harness plugged into the head (the bottom wiring harness in this image) is a 24 pinout connector. The connector seems to have the same pinout as the 2020 civic connector shown here.
![Image]()
I used 16 gauge speaker wire to tap pins A15-A18 (front left and right speakers). Here is a photo of the tapped 24 pin connector.
![Image]()
After tapping this connector, we routed the speaker wire into the left side of the dash, over the top of steering column, and down towards the left side trim. It helps to tape a thin piece of wire to the beginning of speaker wires so you can fish them through the dash easier. Bend the tip of the wire so you don't scratch stuff.
These picture somewhat show how we routed the wires. (Note the red wire in these pictures is power from battery which I haven't talked about yet.)
![Image]()
![Image]()
We popped the piece of trim near at the front of the driver door to route the cables behind it.
![Image]()
I couldn't get a picture of the wires routed above the steering column. Sort of have to feel your way through with the fishing wire.
Power Wires
We took out the battery and battery holder to access a rubber grommet that feeds some cables through the firewall. We punched a hole through the bottom of the grommet as to not hit any of the wires:
There are other grommets you could use (e.g. hood release grommet), but this one gave us the most options for discretely routing the power cable through the engine bay.
![Image]()
We attached the inline fuse to the battery holder using a zip tie as shown here:
![Image]()
Note: We did this part as the very last step --- the battery should be unplugged during the install.
We attached the ground wire to a bolt attaching the backseats to the chassis.
Routing to Trunk
This is basically the same as 10th gen civics (see youtube videos).
We routed signal and power cables to the trunk down the left side of the vehicle (underneath the trim and carpet). We tried to keep signal and power cables as separated as possible. We removed the trim at the base of the front driver door, middle trim behind the front seatbelt, and popped the trim by the rear driver door up high enough to snake the wires to the trunk.
Next we removed the middle carpet piece in the trunk (one rivet centered behind the backseats):
![Image]()
We also pulled some rivets on the left carpet (shown in above image) to access that metal channel you see running along the backseats. We snaked our wires through that channel and pulled them out of one of the through holes.
Here is the finished product:
![Image]()
Important Oddities:
Sometimes after reattaching the 24 pinout and turning the car on, the head unit goes into lockout mode. All you have to do is start the car and hold the head unit power button. Also, all the warning indicators on the dash go on (TCS system, low pressure warning) and the dash says something like 'system calibrating, continue driving'. After installing everything, we drove about a mile and the dash reset to normal (all warning lights turned off). It seems certain counters are reset (my MPG rating reset to zero but everything seems completely normal.
That said, the install turned out very clean and is completely reversible barring a small hole through a rubber grommet in the firewall.Signal wires:
My sub has a built in amp that can tap Hi level inputs. I wanted to tap the front door speakers since those seem to provide the most bass (I could be wrong on this as I only used my ear as a reference). To find these wires, we popped the panel behind the head unit. It pops right off with a plastic trim lever. There is a wiring harness attached to some sensor? on the trim panel that we disconnected so we could fully remove the panel.
After removing the panel, here is a photo looking down at the backside of the head unit. The bottom wiring harness plugged into the head (the bottom wiring harness in this image) is a 24 pinout connector. The connector seems to have the same pinout as the 2020 civic connector shown here.
I used 16 gauge speaker wire to tap pins A15-A18 (front left and right speakers). Here is a photo of the tapped 24 pin connector.
After tapping this connector, we routed the speaker wire into the left side of the dash, over the top of steering column, and down towards the left side trim. It helps to tape a thin piece of wire to the beginning of speaker wires so you can fish them through the dash easier. Bend the tip of the wire so you don't scratch stuff.
These picture somewhat show how we routed the wires. (Note the red wire in these pictures is power from battery which I haven't talked about yet.)
We popped the piece of trim near at the front of the driver door to route the cables behind it.
I couldn't get a picture of the wires routed above the steering column. Sort of have to feel your way through with the fishing wire.
Power Wires
We took out the battery and battery holder to access a rubber grommet that feeds some cables through the firewall. We punched a hole through the bottom of the grommet as to not hit any of the wires:
There are other grommets you could use (e.g. hood release grommet), but this one gave us the most options for discretely routing the power cable through the engine bay.
We attached the inline fuse to the battery holder using a zip tie as shown here:
Note: We did this part as the very last step --- the battery should be unplugged during the install.
We attached the ground wire to a bolt attaching the backseats to the chassis.
Routing to Trunk
This is basically the same as 10th gen civics (see youtube videos).
We routed signal and power cables to the trunk down the left side of the vehicle (underneath the trim and carpet). We tried to keep signal and power cables as separated as possible. We removed the trim at the base of the front driver door, middle trim behind the front seatbelt, and popped the trim by the rear driver door up high enough to snake the wires to the trunk.
Next we removed the middle carpet piece in the trunk (one rivet centered behind the backseats):
We also pulled some rivets on the left carpet (shown in above image) to access that metal channel you see running along the backseats. We snaked our wires through that channel and pulled them out of one of the through holes.
Here is the finished product:
Important Oddities:
Sometimes after reattaching the 24 pinout and turning the car on, the head unit goes into lockout mode. All you have to do is start the car and hold the head unit power button. Also, all the warning indicators on the dash go on (TCS system, low pressure warning) and the dash says something like 'system calibrating, continue driving'. After installing everything, we drove about a mile and the dash reset to normal (all warning lights turned off). It seems certain counters are reset (my MPG rating reset to zero but everything seems completely normal.
