Audio mute for cell phone

I am putting in a hands-free kit for a cell phone in two vehicles.  A 2001 Chevy 2500HD, AM/FM/single CD and a 2003 Toyota 4-Runner with the JBL stereo, 6 CD changer.   The hand-free systems have a wire ( I believe it supplies +12V)for muting the radio but I have no idea where to hook it into the respective radio harnesses.  Can anyone tell me or point me into the right direction?

Thanks,  

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jc
Wasilla, Alaska

https://www.the12volt.com/installbay/forum_posts.asp?tid=25793&PN=1

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My ex once told me I have a perfect face for radio.

For the GM truck you can use the phone's output wire to activate a relay to open or break the radio's ignition wire (usually green or yellow beide the orange). There isn't a dedicated mute wire for this radio. If the truck has steering wheel radio controls you may want to create a real faancy circuit to duplicate it's muting ability, but the relay way is quicker and easier. Checkto see if the phone's mute output is positive as most are a negative trigger.

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sparky

I don't have the steering wheel controls on the PU, wish I did.  I'm know how to wire in a relay to cut the amp (guess I should have mentioned that) but was hoping one or both of these vehicles would have a dedicated mute wire.   Thanks for the replies,

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jc
Wasilla, Alaska