Originally Posted by shellshocked

You are in luck I did it a few months ago.

Tapping into the subwoofer wiring
The stock subwoofer is located next to the spare tire and has a connector on the top of it you can see. There are four wires. The stock subwoofer is a dual coil so the four wires drive the two voicecoils. The two left wires drive one coil and the two right wires drive the other coil. Tap these wires to connect to your amp. I used an amp with speaker level input (MTX5601) and also senses the speaker signal to turn the amp on. I don't remember the polarity of the sub wiring but I do remember it would only work one way.

Amp mounting - I tried to fit the amp in the spare tire compartment but the amp I have was too big. I ended up screwing it to the back of drivers side back seat. It looks nice but if you can find an amp to fit in the spare tire compartment (without removing the spare tire) that would work.

Amp power and ground. This was a little tricky. The battery has a nice terminal where you can bolt on the power wire. I mounted the fuse to a sheet metal bracket you can see when you take the battery cover off. Running the power wire was a little tricky. Open the hood and on the passenger side firewall you will see a small plug next to where the main wire bundle goes through the firewall. I had to remove the plastic cover that sits across the front of the windshield and under the windshield wipers. I had to take the windshield wipers off and remove four or five plastic snaps to get it off but it was fairly easy. This allow you to route the power wire from the battery and reach the grommet on the firewall. The grommet is about 3/4 of an inch in diameter - I cut an x in it and feed it onto my power wire (I use 4 guage from home depot). Thread the wire through the hole downward and you will see it come out in the passenger compartment behind the glovebox. From there I simply routed the wire by tucking it under the plastic trim along the floor carpet.

For the ground I attached to one of the screws that mount the stock subwoofer to the chassis.

For the sub - I just bought one (a nice Kicker) in a sealed enclosure and sat iit behind the passenger side rear seat.

I did have an issue - not sure if it was related to the install. I kept getting a low battery warning on the radio and the car would not start. Try to start it again and fine. Dealer upgraded the firmware in the car and this correctred the problem

OVerall it turned out nice and I can control the sub level from the stock radio.

Originally Posted by shellshocked

My amp has an option for either line level input or speaker level input. In speaker level input mode it can sense and turn the amp on automatically. So I do not use the remote sense to turn amp on. I did however look to see where I could tap and there is a secondary fuse box in the spare tire compartment in the rear and I am sure you can use a volt meter and find a fuse or a blank fuse spot that is powered when the key is on. I have done this on other cars. I simply file a little of the plastic off the top of the fuse to expose the top of the fuse tab and then solder a wire to it and run it to amp - there are several ways to connect if you get creative....