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Amp Bypass For 1999 Sports Luxury

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Hi All.

Firstly, I apologise for bringing this topic up again, I know its been covered quite a few times, but for the life of me, I really dont feel confident in ordering the correct cable I require.

I am wanting to replace the stock headunit, this is the 3rd ive gone through, stuck CDs mainly, now the radio has given up. I replaced the aerial but it didnt help, then I read quite a bit of stuff saying some onboard modules died meaning a rather expensive repair. Im over them now, just want something a bit more "of the time"

Im going to get a Sony XAV701BT.

I know I need to get an amp bypass cable, but I cant seem to find one that states it supports a 1999 model. The one I think is closest is this http://www.dynamicsounds.co.uk/autoleads-pc21054-lexus-is200-is300-amplifier-bypass-wiring-harness-adaptor-p-11086.html

but it says

Wiring Harness Adaptor suitable for the following Vehicles:

  • Lexus IS200 : 2001 to 2004 (Amplifier Lead)
  • Lexus IS300 : 2001 to 2004 (Amplifier Lead)

Can someone please advise me as to the correct cable to get? Ideally the company I would buy it from would also sell a facia kit so I can save on shipping.

Thanks for any help


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I had an After market head unit in my is200, I just bypased the factory amp and just wired from the after market head unit to the speakers. (spliced at the factory amp under the glove box).

Also Where are you located i have a facia kit i been wanting to get rid of for years. i can post it out to you if you want.

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Did you have a wiring diagram you worked form? from all the photos ive seen, the space to work with where the amp is tight! did you cut the connector that goes into the amp? or connect to it somehow?

know of any how too's online with photos to step me through? id be confident to do it, but a starter always helps!

Im in Newtown, Sydney.The facia sounds great (assuming double din?). what sort of money you after? send me a PM with details.


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No i didnt have a wiring diagram. I figured it all out my self. If you go to ryda on parramatta rd at petersham they will install it for you in about half an hour. The facia kit is double or single din compatible. Ill pm u some details.

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Hey Dave,

Dont know if you sorted this one out or not. I have ugraded the stock stereo as you want to do in my 2000 lexus is 200 sports luxury. At first I spliced all the wires and soldered wires to the connector from the amp but after unplugging it once or twice it started to fall apart, so bought the wiring harness separaetly. (its worth the money just to buy the pack from ebay with both.

The first step I see is getting a facia from ebay + the wiring kit in a pack, usually shipped from the UK and take a week or two. I got one like this. (The 2nd link you provided is what I bought) but ill post again to confirm.


The second step is to glue up the facia plate with super glue and screws provided in pack and sand down, paint to give it a smooth stock looking finish. (I believe the smooth finish is well worth the effort in my opinion) Unfortunatly it appears the guy (DJ Wozza) that provided the walkthrough is banned. He did post here though http://www.lexusowne...showtopic=46881 check out post number 8 to see the comparison between leaving the facia stock or modifiying it. In a nutshell, glue it all up according to instructions included. Use an asortment of sandpaper ranging from 600, 800, 1200, 2000 grit then finish off with wet and dry to sand off the bumps on the facia, prime it with grey arcrylic spray paint then finish with satin black, You only really need to paint the front as the rest you will not see.

Third step would be remove the stereo.

Fourth, Remove the glove box and you should see a silver lump of metal, this is the amp. Unplug all wires and remove it. As you can see in my picture I removed it, this means its not in the picture but you will see yours there, but a lot of people do not do this. Its very hard to remove and takes a lot of fiddling around and jiggling to get it free.


post-5985-0-40444200-1356764287_thumb.jpFifth, plug in the white end of the wiring harness loom you buy off ebay into the amp wiring connector (you can see this in the bottom left of my picture. Run the wiring loom up around the top of the glove box and make it come out where the stero got removed from. Youll need to cut the other end of the wiring loom your bought (the back and moroon connectors) ill try to find you a wiring diagram for the harness to connect to your stereo. abviosly you need to look at your stereo wiring diagram and compare colours with the one ill try to find.

Id replace all your speakers. the lexus technically has wiring for 8 spears as the woofers and rear speakers are actually one physsical unit. I replaced with 4 pretty standard jvc speakers.

here is the wiring diagram, check out this post and in particular post 8 http://au.lexusownersclub.com/forums/topic/10528-is200-stereo-wiring-diagram/ i believe you need 8 speaker diagram. you will be mostly interested in the right hand side of the diagram WL & WR refer to woofer.

yeah another problem if you replace speakers is making or sourcuing bessels for the rear speakers to raise them up. if you want more details about stuff i should be able to help you if you want.

here is info about the bessel to make. http://www.tezzaworld.com/viewtopic.php?f=12&t=19

aparently if you only bypass the stereo without changing the speakers as well (especially the rear) the sound will be very bad the rear woofers are 2ohm and the rear speakers in the same assembly are 4ohm. just get back to me if you want to do it yourself. i work slow but it tooks me a good couple of weeks on and off doing all the steps, just ask if you want more help. i had fun going through it all. it took a lot of searching online.


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sorry for the late reply Jak. been away. All makes good sense, thanks for the great detail. Ive got the cable on its way from the UK now. headunit and facia should be waiting at work when i return next week. I think ill leave the amp in situ as I dont really need to get rid of it, and it means i can return it to factory if need be.

Thanks again for your response. ill let you know how i get on.


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  • 2 weeks later...

Hey Jak.

Got the bypass done, all seems to work wel... accept!

The rear speakers just sound like they have bass onl coming from them. Ive been through the manual and it doesnt seem to be anything related to a setting in the headunit, so im at a loss? It was a sports luxury model, so Im not sure if there was something else I need to do.

Any thoughts?



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Hi Dave,Ive had a look at my wiring again. First off Id just like to confirm a few things so I know we are talking about the same thing. Like I said I have a 2000 Is200 Sports Luxury so we should be dealing with the exact same wiring as each other.

Please confirm:

  1. You have unpluged 2 cables from the stock amp (one small and one big)
  2. You Plugged the amp bypass lead into the big connector, that then follows around to the back of the stereo, and you probably needed to cut the other end of that to connect it to the relevant wires of your stereo.
  3. At the white connector side you should have

    1. Violet & Pink connected to White & White Black
    2. Lime and Blue connected to Grey & Grey Black
    3. Yellow and Black connected to Green & Green Black (this is a loop connection on the bypass)
    4. Yellow Red & White Black connected to Green & Green Black (this is looped but wires should go to stereo from this connection as well)
    5. Red & White connected to Purple & Purple Black (this is a loop connection on the bypass)
    6. Red Yellow & White Blue connected to Purple & Purple Black (this is looped but wires should go to stereo from this connection as well)
    7. Then blue and grey to red and yellow which i believe is power constant and aux power or something
    8. Then at the other end should be to your stereo (make sure the +ive and -ive are connected right)
      1. White to White
      2. Grey to Grey
      3. Green to Green
      4. Purple to Purple
      5. You have other wires like antenna, illumination and that which i would connect up as well to your head unit

This is my theory which I have read elsewhere.

The sports luxury has 4 pairs of speakers which totals 8 speakers. 2 Tweeters, 2 Regular Fronts, 2 Regular Backs and 2 Woofers. The rear speaker assembley which is a standard 6"x9" size has been specially designed to incorporate 2 speakers. (The one speaker assembly manages to fit 2 separate speakers into the assembly, the woofer and the regular speaker.) The regular speaker is normal 4ohm resistance but the woofer is 2 ohm. The less the number the less resistance and the more power it receives which i suppose means bigger sound from the woofer. Equally it needs more power to operate the 2 ohm.

The problem you now have is your head unit is mostly likely only supplying power at 4 ohm (most head units do 4 ohm) and its trying to power both a 2ohm woofer and 4 ohm speaker at the same time. This is why Lexus put that special amp in there to accomodate for the speaker setup.

If you wanted to test my theory, disconnect the wiring bypass and run a long speaker wire, connect from back of stereo Geen to Black then Green Black to Yellow. Do this by shoving the wire into the connector that runs to the speakers. This should give you the clear sound you desire. Then try Green to Black White then Green Black to Yellow Red, this should be giving you your bassy muffled sound you dont like. Again by shoving into the connector.

Essentially you want to remove the looping of the green and purple wires in the bypass but connect them in the other termonals to go to the speakers because the bypass seems be wired to want to go the the woofers primarily, then it loops over to the speakers.

The only solution is to try and wire it up as above or replace the rear speakers with normal 6x9 and you dont have to do any wiring adjustments. This brings another set of problems but nothing thats impossible for mounting regular speakers with that bessel. This is why changing the head unit in a Lexus such as ours is not a simple job and one things leads to another.

As I said I just opted to buy 4 new JVC speakers and head unit, disconnect the tweeters and just run a normal system with 4 speakers. I actually have a sub and amp as well but this was not hard to install along with the rest.

Anyone who wants to correct or add to what i said can do so. I learned by doing.


Please post some pics of your install would be cool.

Here is a picture of my finished head unit. Sorry its a little blury.




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Hi Jak.

Thanks for the very detailed response. Heres what Ive learnt. I sorted tried what you recommended, instead of running a long speaker cable to the rear speaker, i got one of my bookshelf speakers from my house and connected that to the rear output from the new headunit. I was shocked to hear exactly the same "bass only" sound coming from the book shelf (its rated at 8ohm) so I thought there must be some setting in the headunit that would cause this. I then found a setting sony call "Rear Bass Enhancer" this doesnt enhance your bass in the rear, all it does is turn off any mids or treble from getting to the back speakers!!! so lamn. So, now that I discovered that, I tuned it off, plugged the bookshelf back in and low and behold, full range! re-wired up the rear speakers, and its now full range.

I think the biggest issue I have it seems is the technology of sound in cars has changed so much since I last really paid attention. It seems that the front speakers are now the most important set as they build the sound field up from them to mimic the idea of how you have your speaker positioned at home, this seems so bloody obvious now, but I used to always have the sound biased to the rears.

Guess its just something Ill have to get used to.

Either way, it seem the bypass works as it should, its just me being an idiot! Maybe Ill change out those rear one day to get some better efficiency out of them (they seem a little underpowered)

Was thinking of these from Polk MM691 (although they are rated at 2.7Ohm, maybe dangerous with my headunit) or the DXi690 (rated at 4ohm)

with a range of 30hz-25khz (94db) and 35hz-23khz (92db) respectively they seem good bang for buck (round $190 a pair)

Thanks for your help!


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No worries mate. Its funny when something like that happens and it turns out to be simpler than expected. If your still sound biased towards the back cant you just change your head unit surround sound to have more sound at the back? I realise that sounds obvious but just saying.

I dont really know that much about amp and speaker ohm and watts etc so cant help too much there, especially with splits or anything like that.

Glad you found your problem


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