E78 Xbox 360 error code | Tinker Mods
What have you done?
That's right, what have you done? This issue is caused by the GPU vendor not matching. That measn the only reason this error occurred is due to the GPU chip being changed or replaced. If you performed a repair by replacing the GPU, then you used the wrong brand/vendor. You will need to find a correct GPU to get the E78 error to clear off the Xbox 360 console. If you bought the console in this state and do not have the expertise to replace an onboard GPU, your only option would be replacing the motherboard itself.
