amp (under pass seat) have a two stereo inputs ( one from fm radio, second - from cd changer). Inputs - full balanced (+ and - and ground shield). I recomend, connect line in to fm input source. If u connect a unbalanced audio source (+ and shield GND) - u will need audio transformer (unbalanced to balanced). I use a parot mki9200 handsfree and ipod/mp3 source. In diagram = green relay need to duplicate, and connect to amp via a transformers. If my source on car is FM - FM is play. If on Parot i push to "play" - MP3 is starting playing, and fm source is off. If i push pause again - mp3 is stopping, and radio is connect. :) I have CD changer independent, Radio and FM - to. :) Audio signal is perfect via transformers. Without it - no good, "generator sweeping", signal have a distortion , because to connect full signal - need independent plus and minus and GND for shield. https://cimg7.ibsrv.net/gimg/www.clu...d9916c2a29.png

Hi All,
I have successfully wired in an aux 3.5mm audio jack to a first gen LS400 Pioneer head unit via the AM/FM radio audio circuit.
When a music source is connected to the 3.5mm jack, the audio is played together with the radio on both AM or FM channels. To fix this I simply cut the audio channels on the printed circuit board for the AM radio (I don't listen to AM!) so that there is no longer any AM audio signal being fed to the processor.

Therefore, this method converts the "AM" button on the head unit to effectively become the "AUX IN" function.

Here is how I did it:

https://cimg4.ibsrv.net/gimg/www.clu...0984ab0730.jpgOriginal Pioneer LS400 Stereo
https://cimg6.ibsrv.net/gimg/www.clu...9afe296f72.jpgRemove the upper AM/FM circuit board from the radio

https://cimg4.ibsrv.net/gimg/www.clu...d3f8d8f193.jpgLocate TUR and TUL audio circuits

https://cimg7.ibsrv.net/gimg/www.clu...0615cbf653.jpgSolder in your Left and Right audio circuits of the 3.5mm audio jack to TUL and TUR circuits.
Connect the ground wire to a ground point on the PCB (grey wire in pic).

https://cimg0.ibsrv.net/gimg/www.clu...b73d209c26.jpgLocate AM audio circuits AMR and AML.
Cut the tracks on the PCB using a knife to create an open circuit.
AM radio audio will no longer play through the stereo system.

After carrying out these small modifications simply reassemble the head unit and refit back into the dash. Route your new auxilary cable to your preferred location, select AM and connect your music player.

Hi, I was wondering if this method could also work for a 2005 ES330(With Navigation)? I recently bought this which I plugged into the cd changer port on the back of the stereo, but I found that the sound was way quieter when compared to just using the stock radio. Would this method fix that problem? Thank you!

I know this is very old thread but I am planning to do install in my 98 LS400 with Navi (I guess its Pioneer)
Anyone had success with these
https://www.newark.com/nte-electroni...-3a/dp/15M1943

Also if I dont use my CD player at all -- I can just hook RCA cable and connect to BT adapter and stream wireless right? @zazzn @- V - -- would this work for 98 LS400 with Navi as well

Mine has Navi. I guess I will lose AC controls and a whole lot of stuff.

I don't know for certain since i have an SC400 but i dont see why it wouldnt work. You'll just have to find the sound channel wires that run from the cd changer to the headunit. I also recommend doing an aux jack and then attaching something like the Kinivo BTC450 to it. Thats the setup i have and it works perfect. But again this is in an SC400 not an LS.

That's fantastic but I couldn't see the comptability with 98 LS400. Any idea on this?

Check the back of your radio, if it's a pioneer and it has the standard cd changer port it should work. I got a radio out of a camery and it works. Make sure you get the lexus one though becuase the pinout is diff between lex and Toyota but they are the same between all Toyotas and all Lexus.

Hey V, this is an old thread, but did you end up figuring out your wiring for this?

I want to add AUX to my 98 with Nakamichi.

How did you end up wiring everything?

Did anyone ever try this? I too have a '98 LS400 with navigation/Pioneer. Would love to add Aux In, preferably with less effort than the original post indicated. But both of the parts Zazzn linked have disappeared from amazon, and I see no Aux adapter anywhere showing compatible with LS400 (there are several for LS430 and LS460).

Is the OP still the 'state of the art' for this capability?

it works
 

I did this on my 98 w/ Pioneer and no NAV and it worked (with a small caveat). Like you, I was unable to find any option that's plug and play.

For my setup, I followed OP's wiring as he also has a 98 non-nav, pioneer system. I don't have a need for the CD changer so instead of using the relays to go back and forth between the Bluetooth input and the CD changer, I just hard wired my bluetooth adapter to the plug going into the amp (as shown in OP's original post). I did what zazzn said to do here:

It works great and has crystal clear quality but I can't listen to any other sources (AM/FM/Tape) unless my bluetooth adapter is powered off. The signal from the adapter seems to be overtaking all input sources (I can hear my bluetooth audio from AM, FM, Tape, and CD). Interestingly, it's not totally disabling those sources, though, because I can hear audio from the AM and FM radio when I turn the volume way up and have nothing playing on bluetooth.

​​​​​​​I have not investigated further but the easiest fix would be to add a toggle for power to the bluetooth adapter. I'd prefer not to do that but without a proper wiring diagram I can't fully understand what might be going on.

It still sounds like a lot of work, and I do like to use the radio as well as bluetooth. I think I'll stick with the FM transmitter in the cigarette lighter - not quite the same sound quality, but good enough.

Thanks, ubermn.