I realize this is an old post but hopefully you are still around...
Short in amplifier - did you get this fixed in the end ? Your note below suggest you did replace the amp with a known good one and is still exhibited short - is this correct ? I have same problem. I suspect it is likely a similar component failure.
Short causes Radio1 20A fuse to blow - this results in no sound, antenna does not rise but audio LCD display still works.
I would rather fix original amp if possible/practical ?
BTW - I am happy with sound and clarity of the original amp and dont want the hassle of replacing it with aftermarket.
Do you have any sound at all? when you say booster do you mean the inline amplifier that powers the subwoofer?
The best thing you can do is get rid of the pioneer stereo and fit an after market stereo. I have aftermarkets amp as well with new subwoofers in the boot of the car. I removed the standard subwooferand used this hole as a port. I srill use standard speaker system for mid range vocal and tweeters are standard also.
Remember your sound system is 11yrs old now! Update it!! You will love the difference!
Here is the wiring diagram you requested. You will need Adobe Reader to view it! Lexus LS400 Wiring Diagram
I have a 94 LS400 and get no sound at all from any of the audio components. The audio system seems to work normally according to the LCD display, just no sound. I took car into Lexus and they diagnosed a short in the amplifier. Rather than paying them another 500 for a new amp, I bought one on Ebay. This amp unit is located in the trunk near the antenna mounted. I did a remove and replance and no change. I think the Lexus service department mentioned that the amp was located under a front seat. I have downloaded the audio wiring diagram but still cannot determine if a component is actually under the seat. It is the standard Pioneer system. Any thoughts would be appreciated.