I want to find a wire on the stock lexus ls460 system that goes live when bluetooth calls are in progress. Is there any such wire I can tap into? This is a mark levinson system, if that makes a difference.

Reason I want to do this is to run a relay to turn on some electronics on while I am on the phone.

 

None of the audio system diagram websites I use appear to have diagrams for the LS460. If you can get hold of an diagram for your LS ML system, look for a pin on the amplifier labeled "TMUT" (i.e. telephone mute). It has been standard procedure for the TMUT pin/wire on Lexus vehicles to go to ground when a phone call is in progress so that the radio/CD/etc. are muted. If you can't find a free audio system diagram, a $15 short term subscription to https://techinfo.toyota.com/ should get you a diagram.

 

Excellent -- Thanks for the info and pointer!

I will check out the techinfo website and search the diagrams for a TMUT wire or something similar.

 

maybe this can help in your quest to be able to switch thing on threw bluetooth

http://cgi.ebay.com/Bluetooth-Relay-...ht_2485wt_1135

 

That's a very cool device! Almost exactly what I need...but not quite, I think. This relay triggers when the phone is present, but I need something to trigger only while a call is in progress. It may be impossible for a secondary BT device to do this, since the BT protocol may not have a mechanism to inform a second paired device (the relay) that a call is in progress on the first paired device (the lexus nav). But, this is definitely something to look into. Thanks for the link.

 

I've pulled up the audio wiring diagrams for the LS460 from your link. I've found a couple possibilities.

First of all, there is a TMUT line. This goes from the Mayday ECU to pin 24 on the trunk-mounted amp, as shown in the below diagram clip. The Mayday ECU is I believe something used for the Lexus Link emergency call system, and is not associated with bluetooth. Looks like it is for muting the stereo when placing emergency calls via the Lexus Link system. So, I probably can't use it for my trigger, since the output signal does not come from the bluetooth system.



On the same picture above you can see a "MUTE" input on pin 1 of the trunk amp. This comes in from the dash receiver. This would seem to be just a regular mute line associated with the mute button on the stereo; however, it might also be used by the head unit to silence the music while sending phone audio or navigation audio to the amp. If so, this would be the perfect line for me to use as a trigger. I'll have to do some testing.

Finally there are dedicated lines used for navigation interactive voice audio output, coming into pins 14 and 15 of the trunk amp, as shown in the below diagram. These might also be used for bluetooth phone call audio, in which case I could tap into them and attach an audio sensing trigger relay device such as this one:

http://www.davidnavone.com/cart.asp?14&pid=169

This might be a problematic approach, for a couple reasons. First, the navigation voice signals are low level and may not be strong enough to trigger the sensing relay. Second, phone calls are sparse signals; there are are long periods of time when there is nothing being output on the audio line, i.e. when I am talking and the other person is listening. So this approach will only work if the sensing relay is sensitive enough to be triggered by the just the noise floor on the (already low level) audio signal line.

 

The violet mute wire is the one you want for your bluetooth. Taking it to ground will kill all audio from the HU to the amp.

 

This is the opposite of what I want. I don't want to mute the stereo, I want to find out when the stereo is muting itself from a phone call. Is the violet wire used by the stereo for this purpose?

 

That's how it works on my GS.

 

Perfect. Thanks for the confirmation!