I recently purchased a used 2020 LT3, which according to service records had a brand new amplifier for the 14-speaker system installed immediately prior to my purchase. Good news I thought, since that was one of the biggest complaints I'd seen about the cars in my pre-purchase research.

Unfortunately after some driving on dirt roads I was saddened to discover that this new amplifier didn't appear to have solved the audio issues they were apparently trying to sort out. It was fine for me during the test drive/inspection and during the ~200 mile drive back home on highways, but once I got to driving up and down my dirt road a few times I noticed intermittent problems where it would cut out until I hit another wash boarded section of road. Same thing when I took it to a fun night at the local drag strip - audio fine on the drive there, as soon as the first launch occurred it died for the rest of the night.

The good news is that I found out the true root cause of the problem and it actually was a surprisingly easy DIY fix, so I wanted to share for anyone else who might encounter similar problems in the future with intermittent audio.

Connection going in and out like that, especially on rough roads or bumpy driving situations (such as launch control on a prepped surface), usually indicates a bad ground connection. Peeling back the carpet at the front of the passenger footwell to expose the mounting plate for the amplifier I discovered two things. First, the two nuts attaching the bottom of the mounting plate to the floor of the vehicle were missing. Second, one of the cable connectors plugging into the amplifier (on the right side towards the bottom, from the perspective of the passenger's seat with the mounting plate still attached) had its connector lock disengaged and was slightly loose.

Re-seating the cable and re-latching the connector alone did not resolve the issue, and with some measurements from a multi-meter it appeared that the mounting plate itself is part of the amplifier's ground path going through the two threaded studs on the floor into the vehicle's chassis. With the two nuts that attach the mounting plate to the floor of the footwell area missing, the plate was able to shift slightly during vibration causing it to occasionally lose its connection to ground through those threaded studs if the edge of the slot on the plate wasn't up against a stud.

Replacing the missing nuts with a pair of M6 nuts and some washers did the trick and perfectly resolved all of my intermittent audio issues. If you're having trouble with the same thing in your vehicle, I highly recommend checking if those nuts might be missing for you as well and/or removing them and using a wire brush to make sure the contact surfaces of the nuts and washers down there are free from any corrosion for a good connection to ground.