Hello, I think there something wrong with the amp inside but i don't know what's wrong with it. I didn't see any burn or damage. I send it for a replace and still got this same problem. I can play the amp without running the engine. When i turn on the engine and put the stereo on. The amp show protect mode while it on. The sub will not play. Evething thing else on the stereo work. I try chaning the sub, unplug RCa, and disconnecting the speaker wires and still same problem. It kinda weird to me. The amp show on while it on protect mode..