I recently purchased a Sony CDX-GT550UI CD receiver for my car. I got it with the intention of using its rear unilink port as an AUX port (for a SIRIUS PnP unit) with a simple adapter obtained from another online retailer.

I received the adapter. One end connects to the unilink CD changer port on the back of the Sony receiver. The other end of the adapter is a regular set of red/white female RCA jacks. I then connected the SIRIUS PnP radio to this adapter (via a regular male RCA to 3.5-millimeter stereo mini plug).

Now, I thought hitting the "SOURCE" button would somehow bring me to the rear AUX item. However, I was never able to get to it. It would only cycle through CD, USB, FM and FRONT AUX. I'm thinking since this adapter only plugs into the unilink port and nothing then connects into its "BUS-IN" ports, that is the reason I am unable to get to it or hear anything.

Any suggestions or methods to somehow "trick" it into recognizing what is plugged into this rear AUX adapter?