I have a 2022 Lexus IS 350 and recently my sound has been going in and out. It started yesterday there was no sound, I was unable to use the volume buttons . no radio &no aux sound. I turned the car off then the sound came back on. Heres the weird thing, the sound works PERFECTLY fine if I have the car on without the actual engine being started. Once I fully start the car, my sound cuts out. Please help me identify this!! Im not sure if I hit a button somewhere or if this is a bad amp (Ive been doing research online) my thing is, if its a bad amp..why does the sound only work when the engine is off?

I also ran a diagnostic test and received B15C3 and B15DB. I purchased the vehicle from a Ford dealer &it looks like the previous owner had a speaker installed but removed (there are wires in the trunk sticking out) will this void the warranty? I do have warranty still but also want to make sure this would be covered. Thank you.