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Discussion Starter #1
Thanks to ItalynStylion for this write-up.
I’ve had a lot of people asking lately about modding the IS300’s audio system since most of the stickies are broken dead end links. I have decided to do a write up of the steps for doing an entire system overhaul which consists of aftermarket…headunit, front speakers, rear speakers, amp, sub, and new speaker wires.

DISCLAIMER: Some of these pictures and posts aren’t mine and are being used for instructional purposes only. I have merely attempted to compile all the information I know and information found in various threads so that you guys don’t get pwnt by installation bills $ :blush: If they are your pictures or posts and I didn’t reference you PM me so I can give you the credit you deserve.

Before I get into it let me just say that as a word of advice it would be better to do everything at once. I would be in your best interest to get it all done while you have the car stripped so you don’t have to take everything apart again. Another reason for this is because some of the components are dependent and wont work without the others (Ex: speakers being useless without an amp)
Make no mistake though, this is a very time consuming project that WILL take all day so set aside an entire day if you can.

-Screwdrivers (Phillips and Flathead)
-Ratchet/Socket set
-Wire strippers
-Box of sandwich bags (used for holding bolts you remove so you can find them later)
-Front speaker baffles (see step 5 )
-Rear speaker baffles (see step 6 )

Step 1:Preparation
Roll up your windows. Remove the bolts holding the front seats in but DO NOT disconnect the harnesses under the seat. It would be wise at this time to remove the headrests and to position the seat in such a way that its geometry makes it easier for you to get the seat out of the door opening. Disconnect and remove battery, as well as the battery tray. To safely work on the car the battery needs to be disconnected and if you don’t want to pop a side airbag you need to do this before you move on. By removing the battery tray you will also gain access to a great spot to get an amplifier power wire through the fire wall which we will get to later.

Step 2:Stripping
Get as much out of the car as you can. Let me tell you this makes the job soooo much easier as you progress through the install. Here is a list of things that I would suggest taking out in the order that I would do it and how to get them out…

Front seats-4 bolts at each corner of the seat and a maximum of two wiring harnesses underneath for heated seats and side airbags.

Rear Seat Bottom- The bottom pad must come out first before the seat back. The pad comes out by grasping under the pad closest to where it is attached on either side (pictured below) and pulling up. The pad snaps in and is difficult to pop out, this will take some force.

Rear Seat Back- Remove the headrests. Once the rear seat bottom is out the bolts that hold in the seat back are exposed and accessible, remove all four bolts. Then grab the seat back and slide it up against the metal backing to get it out of where it slides in and is secured at the top. Add it to the pile of car parts you are making.

Rear deck- Now that the seats are out you can get the rear deck off which will allow you to get to the 6x9’s. First remove the C-pillars on both sides.

Under the plastic clips on the rear deck there are bolts. Remove them.

The rear deck should now slide up and out toward the front of the car. Add to car parts pile.

Front Door Panels (long I know)- Start by removing the tweeter cover located by the mirrors. They come off by pulling straight out toward the middle of the car. Next remove the screw hidden behind the door handle. The only other screw is located in the grasping part of the door armrest, remove it too. The plastic trim piece where you removed the first screw by the handle needs to come off. It clips on above the lock mechanism and below where the handle hinge is. Carefully using a flathead screwdriver insert it between the top of the lock mechanism and the trim piece and use it to lift up the trim piece while you pull it off. Do the same on the bottom if it doesn’t come off by only doing this to the top. Now the door panel is held on only by a few pop in clips that are close to the perimeter of the door panel. If you can get a hand under the edge of the panel run it around and gently pull out popping out each clip. Then the panel needs to slide up and off the window sill. Now the only thing connecting the door panel to the door are a few wiring harnesses you need to take off.

Dash- Take the glovebox out by squeezing the sides and allowing it to open all the way out revealing the bottom hinges. Remove the clips that form its hinges by squeezing the ends of the clips and pushing them out. Next, pop off the lint tray on top of the dash which will reveal two bolts. Remove these and pull the out the tray/vent combo piece toward the rear of the car. Then pull out the heated seat and TRAC button housing that sits in front of the shift knob. Now you have access to the four bolts, two on top and two on bottom, that hold in the stereo and temp controls unit. Remove them and lift out the unit undoing the wiring harnesses as necessary.

Other Trim Pieces- Take out the fuse box covers that are on the sides of the car near the front passengers feet. After this pop off the trim piece that is under the seat belt on the B-pillar. Now remove the door sills on all four doors so you can later unclip the carpet to run wires under it.

Step 3:Run Your Wires
Run your wires now so you can just connect stuff as you get it put in. The first obstacle is getting your amp power wire through the fire wall. Underneath where you removed the battery tray there is a bundle of wires surrounded by a rubber grommet going through the firewall pictured below…(thanks to Justwakin for the nice pic)

Cut a small slit in the grommet and push the scissors through to the other side. Now, while the scissors are in the grommet, open the scissors to stretch the opening in the grommet and feed the power wire through. It will come out on the other side up under the dash behind the glovebox in the top right corner. Leave about 18 inches of wire in the engine bay so you can attach it to the battery later. Run this wire down the right side of the car under the carpet. Now run the small amp lead wire from where the head unit will be past the glove box and down the side of the car next to the amp power wire. Both of these wires will come out from under the carpet into the back seat well and through a hole in the rear seat panel that will empty into the trunk where I suggest you mount the amp. The hole exits just above the wheel well cover behind the carpeted covering.
(picture is of the hole on the drivers side of the car but there is an identical one on the passenger side)

The RCAs need to go on the left side of the car so we will run them next. You need to run the power wire and the RCA’s on opposite sides because the two will interfere with each other an create distortion. Start them in the compartment where the headunit will go and run them down under the drivers’ footwell carpet to get to the left side of the car. Then continue to run them down the left side of the car under the carpet next to the door sill. There is an identical on this side of the car like the hole that you used to run the power wire into the trunk so again run them up and out of the carpet under where the rear seat pad and through the hole that leads to the trunk.
The speaker wires for the front doors will be run the same way with the left speaker wire on the left side of the car and the right one on the right. Next comes the hard part; getting the speaker wire through the long rubber grommet that leads into the door. I would suggest popping the grommet ends out of the door and the side of the car that leads into the car behind both fuse boxes. I would suggest compressing the grommets to shorten their length and then push something ridged through the grommet like a portion of a coat hanger with the wire attached to it. Once you get the wire to feed out the end of the grommet pull a good portion into the door. Now that all the wires have been run lets install some shit.

Step 4: Headunit Install and dash disassembly
I won’t go through the steps for the disassembly as they have been we’ll documented step by step with great pictures by a member of ours Chris_Hill. You can thank him for the following link. . .

After you get the old headunit out you need to wire up the new one. Almost all aftermarket harnesses follow the same color code for the wires so it should be uniform but make sure you check what each wire does anyways. The following shows which wires to connect as explained by the forum member, Drinkmalk.
To sum it up, aftermarket wires on the left of arrows, stock radio harness wires on the right of arrows:
Constant power Yellow <==> Cyan with yellow stripe
Ignition Red <==> Grey
Illumination Orange <==> Green
Power Antenna Blue <==> Black
Here is a pic of what you will be looking at...(pic by Squareback modified by me)

This is what it should look like when you are done. This was Justwakin’s car when I did the wiring…the black wire didn’t make it into the pic for whatever reason

Now, after doing this write up I have had several people ask me if there is a way to do this without cutting up the stock wiring and harness. The mentra harness is an option but it's finicky and has some problems. Also, the harness doesnt work on 2001 IS300s. So for those of you looking for another option, here it is. You can buy some connectors called T-Tap wire splices. They splice into a wire without actually cutting it up or having to strip it and you attach your other wire to it....pretty nifty :)
This of course by passes the factory amp and you will need to run new speaker wires. This process is just a way to get around cutting the factory wiring!
So, you would use these to attach the wires from the aftermarket headunit harness to the factory wiring just as I have shown above just without cutting the wires. I myself, always cut the wires just because I know if I wrap the copper threads of the wires together they make a perfect connection so I prefer it. Again, it's personal preference so if you don't want to cut the stock wires these are what you need. Pictured Below....

Obviously if you are running your speakers off headunit power you will need to make the connections from the aftermarket wiring harness to your new speaker wires. I trust you can do this on your own. If not you don’t need to be working on your car ;)
For those running a separate the amp lead wire that you ran needs to be connected to the blue w/ white wire that comes out of the aftermarket harness.

After making the necessary connections to the wiring harnesses and the RCA’s bolt the headunit back into the dash.

Step 5: Front Speakers
If you are going to deaden your car I suggest you do it now when you have the most access to the interior of the door panel. My deadener of choice is and will always be Damplifier, made by SSA
You can learn everything you need to know and more about sound deadening at Sound Deadener Showdown

The front speakers are held in by pop rivets so the only way to get them out is to DRILL them out. Do this and then take the stock 6.5” speaker out. In order to mount your new speakers you will need to make a baffle. The reason for this is that the speakers magnet protrudes to far into the door and the window hits it on the way down. Most people make a baffle out of ¾” MDF which is fine. If you don’t have access to the necessary tools to make the baffles I sell them for $30 a pair just PM me. Here is a pic of the baffles I made...(they have deadener on them too;))

You will need to buy some bolts to attach the baffles to the door and its existing holes and some screws to attach the speaker to the baffle. Connect the wires you ran earlier and you are good to go.

Step 6: Rear speakers
Not a lot to say about the rear speakers. Once you have the rear deck off its easy from there. Like the front speakers you will need a baffle but no one that I have seen makes one that works. You will have to trace your old speakers and cut out a piece of MDF for them. The reason you need it in this case is because the magnet hits the trunk bars below. If you can’t make them yourself PM me, I make rear baffles for $30 a pair as well.
Here is a pic of some baffles Justwakin made…good craftsmanship I do say

You can also choose to put 6.5 speakers in the rear deck in place of 6x9's. All you need to do is make the baffle with a 6.5 cutout like shown in the pic below...yep, that simple! I would only suggest doing this if you are going to add a sub since you will be sacrificing the nice bass that 6x9's offer.

If you choose to you can take the trunk bars out and still retain the trunk lift action by adding some gas lifters like most newer cars have. I wrote a tutorial for that and it can be found here…
Once you have your speakers mounted, connect your wires and move on.

Step 7: The amp
I would suggest mounting the amp in the trunk since there really isn’t a place you can accomplish this inside the cabin. The trunk has that odd little hump in the back which makes finding a nice spot that is out of the way sort of tricky. DO NOT ATTEMPT TO DRILL INTO THE HUMP! It is the top of the fuel tank and you will probably kill yourself in the resulting explosion. Again, as my personal suggestion I would mount the amp to the seat back as demonstrated in my car below. The seat back is ridged and a great place to get the amp up and out of the way. Just drill some holes buy some bolts and bolt her up.

After you connect all the amp wires you are done. But before you put everything back together and discover you did something wrong put the battery back in and test everything out.

. If there is anything I should add or change if I made a mistake let me know. Hope this write-up helps you all!

Now show ya brotha some +rep love ;)

199 Posts
Nice write up. Very useful info. Thanks
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