I have a similar probleem and maybe you can help:
I wanted to use a switch on my matrix modchip for easy turn on and off,
( see --> Tutorial
) everything went well placing the switch.
when I was done I placed the modchip back on the motherboard of the xbox and tested it to see if its working (flashing green led).
so everything was okey and I closed my xbox.
now when I run my xbox i get the service screen with code number 13 ( codenumbers
I had a look to see if the modchip was off, and it was, that would explane why i have the service page because I use EVOx as dashboard on the HD.
so I tured the xbox off, toggled the new switch and turned my xbox back on, now the modchip is working as i see a green led but still I get the service sreen with code numbers 13.
I also have a CD with EVOx on it as backup so I used that to boot my xbox, but then I get the service screen with code number 14.
Im unsure what is wrong and am seeking help.