Cause #1 - While you have removed the Xbox 360 cover and exposed the DVD drive carefully take a look at the laser module. If it appears to be dusty, then blow the dust away using a small fan. If you choose to use a can of pressurized air, make sure you do not have it on full blast, or you could damage something. You could also use a clean cloth to wipe the laser. But make sure you do not touch it with your bare hands.
Cause #2 - If the problem is not a dusty laser, then confirm that the laser module is at the correct starting position. By this i mean that you must make sure that it is in a position that is right under your game disc instead of it being in a position that is outside the disc area where there is no data to read. When you have read the guide on how to fix the Xbox 360 open tray error this will no longer be a problem for you.
Cause #3 – Another characteristic of the open tray error is that when you try to close the tray it spits it back out and gives you the error on your screen. Another possible cause is that the sensors at the back of the DVD drive could have overheated. Excess heat is bad for machines and it is the cause of a good number of malfunctions in many devices. In this case the tray might be getting ejected as a way to stop you from continuing to play while building up much more heat which could lead to more serious problems for your Xbox 360.