Make sure your sub is wired right, the wrong ohm load will kick the amp into protection mode, i have a soundstream 1000si and it is 1 ohm stable, i hooked up 2 8 ohm subs, and 2 4 ohm subs, thinking they were all 4 ohm and it would make the amp get hot and cut off, and eventually make the protection mode cut on. Just an example, but being a 4 ohm dvc sub check the wiring on the sub in the box.