Hello, the part you are looking for is called the Radio amp. It’s located in the passenger side floor in the trunk and when it goes bad you will have no sound. It gets damaged from a defective vent that Lexus installed on all of the ISX50 and ISF and gets water on the amp. If your navagation isn’t coming on that’s the main board in the Navi unit. I’ve replaced quite a few of both parts here in New York where salt gets in those vents with water causing all sorts of amp problems.

 

Thanks for your response.

I do have radio audio.

My navigation has failed,
presumably due to the
Nav Computer (on the trunk).

Please contact me if you
have any other ideas, etc.
Thanks again.