No Warning Tones / Sound not working

[net7]

Hey guys,

I have quite a weird issue going on with the car (2013). Whenever I start the engine, after about 2-5 seconds the sound goes off completely and the car displays a "No warning tones" message. The sound does not work at all while the car is on.

If I turn the car off completely, wait 10-20 seconds, then I start the engine it will work again for 2-5 seconds.

Now... for the somewhat weirder part - if I start the car (ignition only), and keep the engine off the sound works completely fine and does not turn off (at least for the 10 minutes or so I tried).

The issue started about a month ago while listening to music with the car off. The sound magically started working right the day before I had to take it to the dealer for maintenance. However, also coincidentally, all my power ports in the car died an hour or two before the sound came back on.

Could this be an issue with the battery perhaps? From what I've read the car turns off the most non-essential things first if it's low on battery, the radio / audio system being the first.

I'm taking it back to the dealer this Friday, but I was hoping someone could shed some light, I would hate to have to pay for them to check the sound system (not included in the extended warranty) if it's an issue with the battery or something else.