I have a 2008 Pontiac G5 GT and I went to try to install my amp and sub in it and I am getting no sound to my sub at all, my amp is turning on but no sound. I am using a line output converter because I am using the factory headunit, I used http://www.modifiedlife.com/2008-pontiac-g5-car-audio-wiring-diagram/ to hook it up I just don't know what the problem could be.

Has it worked before? Could the converter, bad RCA cables or a few other things have you tested the subwoofers and amp in another car? Really can't tell unless you grab a DMM and do some tests on all the equipment.

The amp was one I took out of my old car the sub is new but i hooked the amp up to the speaker I have sitting in my garage that I know works and it still didn't work so it's either the converter or I have something connected wrong somewhere

redo your connections double check everything..