Pin diagram of the factory radio for the amp turn on wire, needed

I'm sorry to tell you that installing an aftermarket stereo in those is very difficult as the system doesn't use common parts. The controls use a special signal bus between all of the components to turn them on, adjust the outputs and more. As far as I know there are no adapters made to interface with that system. The only way to really replace the factory system is to remove the OEM and wire in everything on it's own. You will lose the steering wheel controls, the factory amp and if it has the rear controls those will stop working as well. Just the way Lexus built that system makes it very difficult.

Just to jump in on this. I am attaching the entire wiring diagram below of the non Levinson system. We do not have actual connector views of the wires but the connector numbers, pin location and colors part of the diagram.

Let us know if you need more info. Thanks

There is no amp turn on wire, that is the problem. It doesn't use a common wire where a 12-volt signal turns it on and removing it turns it off. Instead, it uses a computer signal that turns the power on, and another that turns it off, along with other signals to set the balance and other settings, all on a two-wire network that nobody makes an interface for. Even the base stereo uses those command signals between the units and not a simple on off control like most cars use. That is why Crutchfield even warns not to replace the stock stereo.

That car also has an active antenna that uses a signal amplifier that is also controlled the same way as the audio amp you bypassed. The amplifier uses the antenna on the rear window and without the amp it will barely work. It's why the common work around is to add a new antenna.

Good to hear.