My Kicker DX500.1 is going into protection mode when my sub is hooked up. I thought my sub had gone bad. I have an old sub that I knew was good but when I hooked it up it went into protection mode again. Next I figured the wires to the sub must have gotten pinched some how so I took some extra wire ran it to the amp and hooked up my sub and it went into protection mode again. If I disconnect the positive speaker wire from my amp and leave the negative speaker wire connected it comes out of protection mode and the same if I disconnect the negative speaker wire and leave the positive speaker wire connected. It also does this regardless if the sub is connected or not. The amp is about 2-1/2 years old with maybe 5 months constant use. It was in my summer fun car but I sold it and put the amp in my daily driver.