TCHconn — You might try unplugging and replugging the three connectors at the amplifier — perhaps there's a loose/bad connection. This is easy to do (the black plastic cover is held on by two plastic clips — pull them straight up to remove). This will generate error codes, of course, which you can clear. Make sure that the ground lead is tight too. (Of course, a bad connection might be at the radio end of the harness!) Otherwise, perhaps it's an internal amplifier fault, as you suspect.

Stan