I did a system for a customer with a 99TL. I took the low level signal straight out of the head unit in to a EQ, I didn't loop it back in like most of the guy's on here do. The system works great, but when nav is activated it attenuates the radio but no voice comes out. My assumption is that the nav voice comes into the main harness on the radio and since I'm not using the amp in the headunit theres no voice. Since it still mutes I'm hoping i can add a external speaker to the left front output from the headunit and put it under the dash. I'm looking for input on this idea so I can have a game plan before I take the radio back out cus' we all know how fun that is!Also, thanks to all the guy's that posted all the technical stuff about the stock audio systems, it saved me a bunch of time.

 

Anyone! We'll I guess I'll just try it and I will post what I find out.

 

I remembered someone on this board solving this by using a sony XA-3911 to mute the music to the front speaker so that you can still get the factory navi voice.

hope this helps.