Saturn ION problem

Yesterday I went to wire up a sub amp in this girls brand new ION. I had the power, ground, remote, RCA's, and high to low level converter (speaker signal to RCA signal) hooked up and turned the system on to test it. No go. I double checked each connection and everything was all right. So, to narrow down the possibilities I hooked the RCA's from my car up to her amp and bingo we have sound. I went back and double checked all the connections on the converter and they were all right. I'm hoping it was just a bad converter, but could any of you give me some insight into this delema. I've exchanged the one we used yesterday for another one and I'm going to hook it up today. The reason this is so weird is that I have used these converters several times and never had a problem. Is the ION a common ground system? Or is it something else?If quiters never win, and winners never quit, who the heck came up with the idea that you should quit while your ahead?

No the ION isn't common ground, but the harness is configured different than the 2000 and up Saturns.  The power wire are in the same position but the speaker wires are in different locations.  Do it right the first time