Single CD to 6 stacker

[musicmakere5000]

Hi All,
I have just replaced my Blaupunkt single CD to a Blaupunkt 6 stacker in my VZ sedan. Everything works as normal EXCEPT no sound from the rear speakers, any ideas? The 6 stacker came from a SS Ute, but I would have thought the head units are the same. Anyone help on this?
Thanks in advance.

[barbs]

i believe you need to get the rear channels actived or the head unit settings changed for a sedan - as there is no need for them in the utes.

i think holden are the only ones who do this and i guess they will probably question it