The amplifier amplifies that audio signal and feeds it the speaker output. The wires are not grounded properly, check to make sure the surface is clean, unpainted metal. This can be pretty frustrating as it means your subwoofer level may stay the same regardless of you turning up the volume knob on the stereo.
How do I fix this? I want to keep the look of my truck stock so I may swap out the stock door speakers, tweeters, and center speaker. The place where i got the amp installed said that my oem unit cant be amped. You would just need to hook that up to the remote turn on lead from your aftermarket head unit blue with white stripe. My amp is already installed and I just bought a new sub. I had my installation done by so-called professionals. Could this really be the case.