I have an '05 TL without navigation with about 130k miles. Recently, my speaker system has been cutting out for long periods of time. Stopping and starting the car seems to cause the issue. When the sound is working things seem normal with things like the radio, XM, and handsfree BT sounds coming through the speakers. However, randomly the sound will cut with no warning and no sound is produced when trying the radio, CDs, or handsfree. When the sound is working it might produce sound for a few minutes but sooner or later it will cut out. Furthermore, the radio seems to work fine as the display operates normally with or without sound. I want to ask if there are any known causes/solutions for this. I understand electrical issues can be difficult to find and fix, and this car has had its fair share of electronic gremlins. I have read that the issue might be my amplifier, radio head unit, or maybe the BT module. Any ideas?

 

Sounds like the amp is failing. The most common amp failures are related to bad capacitors. The normal "odd" behavior is buzzing, low volume, fading in and out, or just not working at all. Mine had low volume and buzzing in cold temps. I replaced all of the capacitors and it was back to being like new again. There is a big thread that covers the materials and details of how to do this.

 

I agree sounds like your amp is failing. repair or replace OEM, or go new aftermarket amp

 

Replacing the capacitors in your Amp will breathe new life into your sound system:
It sure as heck put new life into mine! Sounds like the day I picked the car up when it was new.

Even Howard Stern's burps and farts are lifelike again.

https://acurazine.com/forums/3g-tl-audio-bluetooth-electronics-navigation-94/how-oem-audio-amp-repair-fix-buzzing-noise-no-volume-922588/
.
.

 

I had the same symptoms. I picked up an amp for $50 from a junkyard and swapped it in, system works now. Pull off the kick panel under the glovebox next to the passenger door, the amp is held in by 3x 10mm bolts. Top one is hard to access, I used a deep well socket with a wobble extension.