If you have a test light or a voltmeter check for power at the end of the red wire which should be like 4gauge wire with that amp, then check for power at your power cable that turns your amp on from your deck. Then check your ground wire by placing the red lead to your 4gauge wire and the black lead to your ground. If your amp is getting power from the main power line and from your deck wire and your ground is still good, then your amp is bad.