I have a 2005 mercedes c230 sport with the harman kardon system. I recently got my amp repaired by United Auto Radio, due to no sound coming from the speakers. They replaced the processor in the amp and updated it to the newest software version. After receiving the amp back today, and installing it, there still no sound coming from the radio. I see the red light coming from the amp now, but when I move the connector thats unplugged in the picture to plug it in, the red light shuts off. I checked the fuses under the hood, interior driver side dash, but I heard there is one in the trunk according to justanswer.com. I dont know where that one is located.

If anything in the Most ring is down, you'll have no sound. You need a Most loop connector to eliminate the components one by one until the sound comes back. You'll be better off just paying an hour diag at your local dealer.

The dealer wants 2k for the work!