For those having issues with injected Wii or GC games booting to black screen, this happens soon after your WiiU soft boots into vWii mode.
Here are some trouble shooting tips.
External USB HDD:
This one seems to be a common issue that I have come across personally and also with others as well.
Not all ext USB HDD works the same, in vWii mode, it can be picky on the type of USB HDD used. The issue is the USB controller used in the HDD enclosure, it may not be compatible in vWii mode, even though it works fine in WiiU mode.
When you boot up a Wii or GC injected game, your WiiU does a soft reset and boots into vWii mode to launch the game. If the USB HDD handshake or initialisation doesn't happen within a certain time frame, you will get black screen most of the time, if your lucky, the game might boot.
Personal experience, out of 5 ext USB HDD that had and tested, 2 simply wouldn't work and always boot to black screen, 1 would work randomly, and the other 2 works perfectly, all different brands.
There is currently no compatibility list around that I know of as to what HDD is good to use, also USB3.0 HDD is useless on the WiiU and has no benefits, WiiU is still USB2.0.
Try another ext USB HDD.
WiiU USB ports:
For troubleshooting, make sure you have nothing connected to the USB ports on your WiiU and install the injects on your NAND and test. If inject works, then try connecting the ext USB HDD back to the WiiU again and try launching the same Wii/GC inject again that is on your NAND. If game boots to black screen, then you have narrowed it down to the ext USB HDD.
Either remove ext USB HDD and just play off the system NAND or get new USB HDD.
Other Troubleshooting:
- Boot into vWii mode, then exit back to WiiU, then try booting Wii/GC again. For GC injects, try delete the gc config file on the root of your sd card.
- Make sure your WiiU system language is set to ENGLISH if you have it set to any other language.
- Try a new SD Card (make sure you copy all the files from the old to the new)
If all fails, then you have a rare WiiU that simply doesnt want to play nice with Wii/GC injects. I have read a few posts in the past where people have tried the above troubleshooting and nothing works, even factory reset didnt help and there was no solution for this.
Good luck.