Okay, I have one of the HF850 Motorola bluetooth kits, with a stereo mute. Tied it into the OEM Nakamichi system easily using the existing cell phone harness underneath the cup holder. There are two harnesses. The one with three wires contains the mute, 12v and ground. Looking at the connector head on, with the tab part on the top, the right pin (#1) green and white is the wire you tie into.

This wire is 12v+ when the system is on. When it is shorted (tied to ground) the system mutes. You could use this for all sorts of fun.

In your trunk, under the antenna area the old cell phone system should be removed. The two harnesses then tie together. Otherwise you should see two harnesses tied together next to the tire tools. There is a violet wire in there also, that is what goes to the stereo, the other end of the harness goes to your cell phone harness. I will check the schematic and see where you can access this right behind the HU if you want. But this is easier.

Peter

 

Thanks for posting your find. Others will find it useful. I'm guessing that similar mute points might be found in Lexus cars through the 2003 model year after which wired phones were no longer offered as an option. I also found the mute points in my 00 LS under the center console and in the trunk on OEM phone connectors.

Based on the wiring diagram for my LS, it looks like the mute could also be done at the head unit of my Nak. The diagram seems to indicate that the mute is on the amp for the standard and Nav systems. Could be different on the SC of course. Of course, why bother if you can do it at the phone harness.

Here is an old doc showing where I found the mute points in my LS: http://home.kc.rr.com/colchester/pho...%20install.doc