I always wanted to have more bass in my 4runner, so after searching through threads and youtube vids, I decided to pick up an amp and hook it up. Major shoutout to this thread in particular. Replaced JBL Sub/Added Amp: Install Pics/Info

For the amp, I bought a RockFord 250 mono amp. This amp has a high level input with two positive and two negative wires, and magically, the 4runner oem sub has two positive and two negative wires.

For the oem replacement sub, I bought a pioneer 8 inch shallow mount. It bolts right up and works pretty good with the stock jbl amp.

The amp's power is easily connected by running a power wire through the fire wall, to the battery. I ran mine on the driver side under the doorstep panels to the trunk. As for a ground, I used an eyelet connector and bolted it to a random bolt under the trunk carpet. The amp's wire to power off when the car is off is ran to the rear panel's 12v car charger port with a snap lock connector

Sorry for the large photo sizes, I'm still learning how to resize them. and feel free to ask any questions.
anyways. wiring goes like this, with some pics attached. snip off the connectors connecting to the stock subwoofer. The red and black wires are positive btw. the yellow and green are negative. connect those wires to the matching pos/neg wires on the high level input wiring harness that came with the amp. I used some spare 14 gauge wire because the wire given isn't long enough.

Once the high level input is connected, run some cable from the amp output to the subwoofer. The pioneer has two inputs, so just pick one and it'll work perfect. No need to split the wire with a Y-connector or whatever.

As for tucking the wires and reassembling the trunk panel, the sub fits back in the normal spot with the wires pouring out. They will be squeezed by the sub It's probably best to just cut a whole in the jbl sub box, but I was lazy.

Running the wires is up to you, with however neat you want to be. I just found what works for me and tucked them the best I could. The amp just lays in the back of my trunk right behind the seat, so the wires come from just under the side panel and straight to the amp so there isn't a wiring mess.

If you dont want to use a factory sub, like I chose not to after a couple days. You can always get a sub/box. I got a used kicker comp c 10 inch sub in a closed box. Just connect the output wire to the box instead of the oem sub and all works mint.

This was done around midnight after work during the one night San Diego decides to rain heavily, so if I can do it with very little wiring experience, I'm sure anyone else on here can do it better.

Here's some pics of the amp inputs, the connection to the oem sub wiring, and what I bought.

Attached Images

       

I forgot to mention. Along with the bass controller that comes with the amp, you can also control the bass from the head unit controls. Also, if you use the factory sub location, the panels will rattle a lot. At least mine did. That's why I ended up picking up a used sub box.

is that sub a dual voice coil? hope your using both of them if it is.

The box I got has a single voice coil kicker subwoofer. I only used the pioneer for for a day to test the amp before I got a kicker sub.

How has this worked for you long term? I'm looking to do the same thing. Any issues with the wiring or anything like that?

sorry, been a while since I've logged on. No issues so far. 10" Kicker CompVR bumps nicely. The toughest part was deciding where to run all the wiring.