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0020 could be general GPU power error.
Thats what ive always understood that error to be...
So just try loosening and tightening the screws. It should come up good again.
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Even weirder news: received a 360 with 0020, stock X-Clamps, minor cooling mods (nothing harmful; RAM heatsinks, thermal paste, fan shroud). After X-Clamp, works fine, when heatsink is loosened so that it can move roughly 0.2mm, 0020 right away.
Yep, so that pretty much proves the problem is to do with a cold solder connection under one of the chips.
When it comes to chips like the ones in the 360 with BGA solder joints, 0.2mm is a fair way.
QUOTE(MetalMiketh @ Mar 14 2010, 05:39 AM)

I had an error code 0102. I X-Clamped it. Now I'm getting error code 0020.
any ideas what could be doing this?
I made sure the bolts weren't over torqued.
Maybe I put too many washers between the case and the mobo?
Reflow the GPU