no sound from rear speakers

I just installed a Alpine cde-9881 unit in my 93 toyota 4-runner, all 4 speakers work with radio playing, but only the front speakers work when playing a cd. It don't seem normal, so if anybody no whats going on please help.

Are you using an external amplifier?

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there may be a factory amp on that vehicle running only the rears I would check the blue/white wire behind the radio first to make sure it is connected to the blue/white in the harness, my guess is that the blue from the radio is going there and as soon as you change to cd the blue wire (which is the power antenna wire) is no longer sending 12v to turn the factory amp on.

--->Richard

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2008 Scion xB
Pioneer AVIC-D3
RF 3Sixty.2 sound processor
Stock speakers (for now ;))

Hey thanks guys, i'm not using an external amp, just the one in the radio. The blue/white wire from the radio i believe is connected right cause the  pwr. antenna is working. The previous Alpine i had in there did the same thing, and i have this one hooked up the exact same way. What would be the difference between the internal amp output from playing the radio an all speakers work fine and when playing a CD.. just the front work...Humm....I'll check to make sure the suv don't have a amp for the rear speakers. And the mean time if anybody have any subjestions let me know.

Your problem has already been Identified above.  The blue wire is the power antenna wire.  The Blue/White wire is the amplifier turn on wire.  When you are listening to the radio, the power antenna wire is powered to raise your antenna.  When you are listening to a CD this wire goes dead allowing the antenna to go down.  Your vehicle obviously has an amplifier and when you listen to the cd player, your power antenna wire goes dead, thus turning your amplifier off.

Hey guys thanks, i work for toyota an should have figure this out a long time ago, i just did'nt think the rear speakers had amps in them, and the factory radio turns the amps on an puts the antenna up an keeps it up as long as the radio is on.Thanks again.