How to find your error code:
The specific type of hardware failure can be determined by a "hidden" error code
Turn the xbox 360 on, and wait till the 3 red lights are flashing.
Press and hold the sync up button (the small white one), while holding that button press the eject button.
The LEDs will now blink the first number in the code (as described below).
Release the eject button and press it again.
The LEDs will now blink the second number of the code.
Release the eject button and press it again.
The LEDs will now blink the third number of the code.
Release the eject button and press it again.
The LEDs will now blink the forth number of the code.
Release the eject button and press it again.
The LEDs will go back to the 3 red flashing lights.
You should be able to determine the difference between the 3 flashing lights and the error code lights by the rate in which they flash.
Here is how you interpret the LEDs to get the code number:
All four lights flashing - 0
One light flashing - 1
Two Lights flashing - 2
Three lights flashing - 3
0001 power supply problem
0002 power supply problem
0003 (not yet known)
...
0010 over heating
0011 over heating - If you are recieving this error after dissassembling your console make sure to all 8 of the heatsync screws are tightened securely to the board/heatsink holes.
0012 over heating
0013 over heating
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0020 (Not yet known, possibly overheating)
0021 DVD Drive Time out - Can be caused by problems with a firmware flash. This is also speculated to sometime be caused by a problem with the southbridge chipset on the motherboard.
0022 GPU Error / GPU Overheating
...
0101 (not yet known)
0102 unknown error - literally means the console does not know what is wrong. possibly a short or cold solder joint somewhere. So far there is 1 major theory for what causes most of these errors is that the Ram, CPU, or GPU are not soldered properly to the mother board This can be solved by re-Heating the chips DO NOT attempt this if your console is still under warranty. If your console is still under warranty return it to the store where it was purchased or call MS to have it replaced.
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0110 Memory Error / Memory Overheating - see solution for error 0102
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1003 Hard Drive Error... It could be a problem with the Hard Drive itself or a problem with the internal connection to the hard drive, Try removing the hard drive and playing without it
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1010 Hard Drive Error, Can be caused buy a currupt or missing Eprom.
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1013 (not yet known)
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1020 (not yet known)
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1022 AV cable error... There is a problem with the AV cable, try using a different AV cable. (could also be a problem with the encoder chip)
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1030 (not yet known)
From llamma.com