Some of the imports may come with Bose Radio cassette and a 10 CD stacker player. The Radio cassette is not suitable for Australia use and likely that it would have been replaced. I have replaced the head unit with A Clarion system and after some efforts I managed to obtained the wiring configuration for the CD connector and managed to link up the Sony CD system to my Clarion radio cassette. The connection is quite simple, The Sony system has a 5 pin din plug, and by connecting four of the pins ( 1-common ground, 2-right channel, 4-left channel and 5-CD-on) to the appropriate pins in the head unit; everything comes together. If you want to retain the Sony CD system and here is the way.
