Instructions
Turn on the Xbox 360. When the console's three red lights flash, press and hold the sync button on the Xbox 360 controller. Simultaneously press and hold the "Eject" button of the console. The LEDs on your console will flash the first number in the code sequence. If all four lights flash, the number is "0"; one light equals "1"; two lights equal "2"; and three lights equal "3". Determine the code number and write it down.
Release the "Eject" button and hold it again. Watch the console LEDs and write down the second number sequence in the code. Repeat this two more times for the third and fourth numbers in the code. Release the "Eject" button, and it begins flashing three LEDs like in the beginning.
Use the Xbox website's "Secondary Error Codes" listing to determine what is causing your Xbox error. (See Resources)