Same Prolbem as the other guy

there are two things its either your battery or your starter

There is a reset button on the front of the face plate buy the buttons for changeing your radio sations.It is right beside the last button on the right side of the face plate.Take a pin or something with a point on it, To push the reset button in with, Hold it for a couple of seconds,Then it will come back on.There is no code to unlock it, Only if you put a code into it .(But) before you do this (Check) That no speaker (Wires) Come off from the (Speakers) or from the deck some where. If a wire come off make shure to put it back on (Properly) Before you reset it. It can allso go into the protect mode if your car is hit in a (Accident)

unplug the radio harness and check for ground on all the speaker lead's. if there is ground on a speaker wire then there is a problem on that particular speaker and if you disconnect all the other speaker should work if not then i would assume the actual unit is defective

1. Remove the black face screen. 2. The 4 holes on the satellite that hold the face screen on have a rubber stopper in each.  Pop those out with a screw driver.  There are now 4 screws to take out. 3. The front silver face plate is now only held on by glue.  Take a hair drier around the edges to soften the glue, then carefully pry the front face plate off, being careful not to damage it (I pried it from the bottom so any damage wouldn't be noticed).
Note: the 3 screws on the bottom have nothing to do with removing the face plate.

you simply have a speaker shorting in your car. Either an old speaker with a bad voice coil (short) or a speaker who's contact(s) are touching metal. This type of short or grounding will cause the internal audio amplifier to shut off to protect the radio's output circuit. To diagnose which speaker is the culprit, you'll need to disconnect all speaker leads from the radio and one by one re-connect them until the output shuts down again. The safe way to check is with a voltmeter. If you connect one side of your voltmeter to ground and test each speaker wire lead for continuity, you'll hear an audible "beep" whe you find the grounded wire/contact. A professional car audio shop can diagnose this for you if you're still having difficulty. Hope this information was helpful.

my problem as i think was same..
..problem actually not plate...it something inside...
repair guy just fixed something inside...as i understand some condinsators heats and after some pereod of time its broked by himself..so he first was thinking that it was plate but after it he foung the problem in this condensators....actually problem in tape and not in plate...

the security on the radio has been tripped you need to take it to a GM dealer and have them run a code to unlock it CAL means calibrate 

well it seems i have solved the problem but really dont know how.I disconnected the battery hoping it would trigger some sort of reset I guess it did it works again so all is well,thanks for your consideration on this matter.

It could be that the wires in the harness that go to speaker from stereo are not connecting to the leads on the stereo. If this is the case the wires to speakers are not connecting, but the wires from the power source are still good. Try taking the harness out of the back of the stereo that connects all the wires to the leads. Hopefully your wiring is labeled from the factory. If it is it might say "Left front speaker". Isolate this wire and wiggle it inside the harness back and forth. If it moves even a 1/16 of an inch it may be that the leads are not connecting. You can try jerryrigging it by shoving something in their in hopes that it will hold it in place. You may need to replace the harness.

What type of vehicle is it in? Is there a blue/white wire connected?