Back Speakers Stopped Working???!???

I recently had installed a DVD player headunit with the screen and the whole nine yards. Soon there after I realized that my back 2 speakers on the rear deck are completely dead. I went into the trunk to see if the amp maybe was disconnected for some reason but it wasn't. I was wondering if anyone had this kinda problem, or if someone has a clue of how to fix it and what it could be. Thanks alot.

Try this "walk-around test:
1 Turn on the audio unit.
2 Carry out the speaker walk-around test by pressing preset buttons 3 and 6 simultaneously.

This will do a walk-around of all the speakers to make sure they are all working. One option is to substitute other speakers, repeat walk-around test to see if it is the speaker that has gone.

Other than that.. It might be the circuitry, fuse or soemthing..

I tried putting in a pioneer head unit and i have the same prob! i guess the factory amp doesn't work when the oem radio is out.