Sorry but this is incorrect for the model year 2003-2006 standard radios. I have a PAC unit in my truck.
I don't know about the 2002 and at some point they did start actually including the actual aux port on the radio in 2007 or later years?
The aux add on basically hijacks the input port on the back of the radio but requires you to have it turned on. You must have XM radio, external cd or overhead dvd player for this to work.
It has 2 AUX ports on it and there is a switch. The switch determines which aux port or normal operation. But you MUST have the radio talking to one of the external devices for it to work. So in my truck I have to put it to one of the XM radio stations and then it will work. The AUX button on the radio does nothing in this setup.