I just installed a Kicker DXA500.1 amp in my car, and all it does is go into protect mode when I turn on the ignition. It does this even with the subwoofer and RCA input disconnected. I have double-checked all connections, and everything looks good. I am not in the car audio business or anything, but I have installed a handful of amps before and never had an issue - pretty confident I haven't done anything wrong here. I have used 4 gauge cable per Kicker recommendation, the positive and ground connections are tight, the amp is not touching the chassis, etc. The ground connection I am using is the same connection that the car battery uses. I am at this point assuming I have a defective amp. What could I be missing here?