A Klasse audio system issue

There could be many reasons for this. 'Display defective' is not very specific. Is the head unit turning on? Is anything showing on the display? Have you verified the fuses? Speaker crackle might indicate a failing amp, but with complete audio loss and a possible head unit problem, it's difficult to say. Is there a Bluetooth issue? Does the unit try to connect at all? More information is needed for a remote diagnosis.

The unit turns on, and the display is working, showing radio stations and other information. However, there is no sound from any speaker. Bluetooth connection attempts are not happening. The fuses are fine. Where is the amplifier located in this model?

Considering that the head unit powers on and shows information, but there's no audio output and Bluetooth is not connecting, and the fuses are verified, the 'display defective' error probably means an internal failure within the head unit itself. The complete loss of audio suggests a problem with the audio processing stage or the amp section inside the head unit. The amp location is not important if the head unit is broken. The best course of action is to take it to a workshop for head unit replacement or repair.

Confirmed the head unit was faulty. It has been replaced. The audio quality is back to normal. Thanks.