Error DC means there’s a short circuit somewhere. Could be a problem with a speaker or the head unit itself. If it isn’t happening regularly it will be hard to track down. If it is happening a lot, you can start by disconnecting the speakers one by one and see which one is causing the problem. If it still happens after that, it’s probably the head unit. At the minute, there’s not a lot you can do about it. Did water get in anywhere with the rain lately? Something to look at.