I just replaced my stereo on a 2008 Mazda CX9 with another factory original stereo. The installation is fine but I have no sound. I was told it doesn't need a code but the stereo has to be programmed to the car. Anybody who has replaced their stereo know how to do this? Thanks!

 

No programming needed.
Is it a identical stereo?
Why did you replace your old stereo?

 

Did the installer verify before installing that the replacement worked? This should have been done by simply connecting to the harness before installation dash.
Also also was his a NIB or refurbished head unit? In either case the installer should have checked work-ability before installing it>