Yukon Denali XL Speakers not working

[Bigjimmy]

In my 2008 Yukon Denali XL (with Bose system)only the drivers door and pillar tweeter work,no other speakers do anything EXCEPT when I turn on Onstar then passenger speaker comes to life,the rest don't!
Any ideas?
Was going to replace the speakers but strange that passenger one doesn't work with stereo but does with Onstar?
Any advice much appreciated

 

[Bigjimmy]

Nobody?
I was going to just replace all the speakers as it seems to be acommon fault,but seems odd that passenger side works with Onstar but not stereo?