E77 Xbox 360 error code | Tinker Mods
A simple issue at heart
To be fair, this is a fairly straight forward issue. The E77 error on an Xbox 360 console is caused by a failure to read or write via the Ethernet. This means the Ethernet chip is bad and needs to be replaced. Replacing an Ethernet chip is not for the weak of heart. A strong soldering station and reflow gun may be needed, not to mention a matching Ethernet chip. A typical fix for this problem would be replacing the motherboard itself.
