E08: Unconfirmed: General I/O Malfunction, could be caused by an error with any of the I/O devies such as A/V port, USB, Hard drive, DVD drive, etc. over torquing of the AV or heatsync bolts can cause this error.

I found the secondary error code and i dont understand what i have to do

On the xbox360 hit the eject button and sink button it will have 4 numbers its pretty basic

0 - all lights flash
1 - first player
2 - first and second
3 - first second and third

Then compile the numbers so we can help you better my xenon had 0102 which is cold solder joints I had to reflow my GPU and replace my clamps.

i got a 0020 and i dont know what to do

Known fixes:
1)If you worked on the mainboard recently(soldered or so) remove these wires because you might be drawing too much power from the GPU
Also look for missing/bridged components like capacitors/resistors
2) If you jtagged the console remove wires and resistors, the parallel port can stay as long as no PC is connected.
3) X-Clamp replacement
4) Flush with alcohol, let dry, begin Relow with flux like below
5) Reflow GPU (and RAM if this fails) area
6) Reball the GPU and RAM, for bridged solder