Lexus Is300 2000/2005 Aftermarket Radio Install Without Aftermarket Harnest ..

1} First Thing You Wanna Do Is Locate The OEM Factory Amp ... Then You Want To Find The Wires For Speakers
( FL , FR & RL , RR ) Or If You Want To Add Sub & Tweeters You Can Find The Speaker Wires .. 

2} This Plug Is The One That Comes Out Of The Factory Amp For The Speakers . That Has The Speaker Wires You Need To Connect To The Back Of Your Aftermarket Radio . DO NOT USE THE FACTORY RADIO WIRES ONLY USE FACTORY AMP SPEAKER WIRES ! OR IT WILL NOT WORK !! 

3} Now You Need To Find The Power 12V , Ground , & Illumination Wire From Factory Radio Harnest Wires .. 

( 2005 Lexus IS300 Car Stereo Radio Wiring Diagram )

Radio Constant 12V+ Wire: Blue/Yellow
Radio Ignition Switched 12V+ Wire: Gray
Radio Ground Wire: Brown
Radio Illumination Dimmer Wire: Green

( 2004 Lexus IS300 Car Stereo Radio Wiring Diagram )

Radio Constant 12V+ Wire: Blue/Yellow
Radio Ignition Switched 12V+ Wire: Gray
Radio Ground Wire: Brown
Radio Illumination Dimmer Wire: Green
( 2003 Lexus IS300 Car Stereo Radio Wiring Diagram )

Radio Constant 12V+ Wire: Blue/Yellow
Radio Ignition Switched 12V+ Wire: Gray
Radio Ground Wire: Brown
Radio Illumination Dimmer Wire: Green

( 2002 Lexus IS300 Car Stereo Radio Wiring Diagram )

Radio Constant 12V+ Wire: Blue/Yellow
Radio Switched 12V+ Wire: Brown
Radio Ground Wire: Gray
Radio Illumination Wire: Green

( 2001 Lexus IS300 Car Stereo Radio Wiring Diagram )

Radio Constant 12V+ Wire: Blue/Yellow
Radio Switched 12V+ Wire: Brown
Radio Ground Wire: Gray
Radio Illumination Wire: Green

Now You Want To Power Your Aftermarket Radio From The Factory Radio Harnest Wires & Then Hook Up The Factory Amp Speaker Wires To The Aftermarket Radio Speaker Wires ! AND THEN YOUR ALL DONE ! 

#YOURVERYFUCKINGWELCOME !!!!!