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Discussion Starter #1 (Edited)
It seems alot of ppl are asking for this, so here it is.
It is based on a 2001 since I have an 01.
Edit 6/27:
I just looked at the wiring diagram for 02+ The wiring color are the same, so this works for all IS 300

From OEM radio harness:
Ground: Brown
Constant 12v = Blue yellow stripe
Accessory (switched 12v) = Grey
Illumination = Green
OR
From cig lighter plug:
Illumination
Most of the time illumination is positive = green with silver dot
If that doesn't work then you need negative, use the green with white stripe.


From stock amp harness:
Front Right speakers:
Light green +
Light blue -

Front Left speakers
Purple +
Pink -

Rear Right speakers (high, not the woofer):
Red +
White -

Rear Left speakers (high, not the woofer):
Black +
Yellow -

You do not need to remove the stock amp to get to the wiring harness. Just take off all the bolts and pull it down a bit. It's really cramped up in there, and it's a pain in the f***ing ass to get in there.

Be sure to unplug all of the harness that feeds into the stock amp.
The harness is located on the far side of the amp (near the engine)
I believe there are 2 harness. If you do not unplug all of them, it will blow your after market stereo fuse!

T tap all the wires from the stock amp harness and run it to the head unit. There's enough space to run it right underneath and behind the glove compartment. Be sure to mark the wires so you wont forget what they are.

I highly recomend replacing the rear speakers, although it is not necessary since the high of the rear speakers are safe 4ohms.

If you are replacing your rear speakers, then I suggest running speaker wires directly from your aftermaket head unit to your rear speakers.

btw.. I didn't figure all this out by myself. Almost all of the info are here on the forum. I added more info and consolidated. So thanks to everyone here.
I finally contributed, I can die a happy man now ;)

Good luck. Turn this into a sticky please.


nice huh? ;)

---
- Prescription eyeglasses for less at PaylessForGlasses.com -
 

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+rep for taking the time. Be nice to see the '02+ version too.
 

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good write up man, +rep for taking the time to go through everything and post it one coherent thread.
 

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From cig lighter plug:
Illumination
Most of the time illumination is positive = green with silver dot
If that doesn't work then you need negative, use the green with white stripe.
I just wanted to add that these wires are also available in the Radio harness. This will save you the time to get to the cigarette lighter plug unless you need to get there for some other reason.
 

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I just wanted to add that these wires are also available in the Radio harness. This will save you the time to get to the cigarette lighter plug unless you need to get there for some other reason.
yea, the green wire shown here. save some time...



damn thats hard to see. its on the left side, u can see where the green wire comes out of, next to my thumb
 

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What do I do if I want to run an un-amped signal to an after market amp that is going to power a sub? Tap it just before the signal enters the amp?
 

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What do I do if I want to run an un-amped signal to an after market amp that is going to power a sub? Tap it just before the signal enters the amp?
That's not gonna work well, you have no volume/gain control over the signal going into the stock amp. Volume is controlled by the stock amp. You'll need to provide you own volume/gain control if you tap into that signal.
 

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That's not gonna work well, you have no volume/gain control over the signal going into the stock amp. Volume is controlled by the stock amp. You'll need to provide you own volume/gain control if you tap into that signal.
So in other words, I should just get a LLC until I get my after market HU?
 

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I don't know if anyone would be interested in this... but I have figured out a way to make a pulg and play amp bypass... without cutting ANY of your factory harness!!!

If there is enough interest I'm thinking about producing this as a kit. Let me know and if you guys want I'll start another thread...
 

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I don't know if anyone would be interested in this... but I have figured out a way to make a pulg and play amp bypass... without cutting ANY of your factory harness!!!

If there is enough interest I'm thinking about producing this as a kit. Let me know and if you guys want I'll start another thread...
Post a pic of it....
 

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You got it. What kind of amp do you have? Maybe you don't even need an LLC, lots of amps have hi-level (speaker) inputs.
Alpine MRP-650. I know of the speaker level input you are talking about. But I tried those with my old amp on the IS and it didn't work... Maybe the old amp was busted?

Anyone use the speaker level inputs on an amp on an IS?
 
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