It could be something in the message board and I do remember something I read about it, oooh, ages ago. Searching for something now.
Maintenance mode is a secret mode that is build-in to every Wii console. Noone knows the real use of it, but sometimes, it seems to be accessible on a bricked Wii. This is why we recommend trying it before trying another method.
* Wii with working Health screen
1. Turn on the Wii and you will see the Health Screen. Now instead of pressing A, hold + and -, then press A. (keep holding till the screen changes!)
2. If you did it correctly (and your Wii isn't bricked enough to ruin it), you will see a message on the screen saying the Wii is in Maintenance Mode.
3. This mode allows you to do everything except using the Wii message board, so make use of that to backup saves or to run the HBC!