Taken from here
SD/USB Loader Error Partition not Found. Most likely have a cIOS installed incorrectly, out of date, or missing. Possibly formatted the device incorrectly or device is not compatible yet.
SD/USB Loader Error Hardware not recognized. Most likely have a cIOS installed incorrectly, out of date, or missing. Possibly formatted the SD card or USB incorrectly, is unsupported, or not enough space.
Q. I have formatted the device correctly and have cIOS 36 rev 8+ but I am still getting this error; how would i fix this?
A. Be sure to have the device hooked up to the Wii before you power it on. You may lack USB support as well. Installing cIOS38rev14 would clear this up.
Wad Install Error Most likely have a cIOS installed incorrectly, out of date, or missing. If a file was needed, then it was not in the correct folder. If you are using cios38rev14 installer, put ios38-64-3610.wad file in the root of the SD card. Each programm needs its files in specific folders, so pay attention to that. Can also be a bad wad or not enough space on the Wii. Possibly formatted the SD card incorrectly.
SD/USB Loader Error Corrupt ISO. Most likely patched incorrectly (you don't have to patch region when using USB Loader).
Unauthorized Device Detected Most likely outdated firmware for your modchip. Possibly an outdated or missing IOS. Update to latest ios249
DVD Read Error / Anti-piracy security Most likely old or missing IOS.
Q. How can I fix this?
Install a newer IOS 249. There is a 002 fix channel that will fix most of the older games, Neogamma r7 is the latest version for now. USB Loader GX,CFG, Uloader are other alternatives.Also mind that some games require alternate dol loading method to play. see this post.
Unauthorized device on 4.2 thanks to N we have abrand new error code... So, no workaround on this yet, try unplugging any chips or whatever N thinks is unauthorized from the wii. Seems like Korean wiis are super defective to this. Some people have reported being able to contact their wii salesman, and complaining to him that it bricked after upgrade, they were able to get him provide them with a new wii. Thi is only if he provided you with a korean wii, and not warning you of the risks. If you did it by yourselves no luck on this..
Installing/Uninstalling WAD's/Downgrading/Region Changing If it's a WAD files ticket just reinstall the WAD and then uninstall using Wad manager v1.3/1.4/1.5. If it's a missing ticket due to a downgrade or region change then you may have a bricked Wii. Try to reinstall all IOS's from original sources then run IOS Downgrader (or dont downgrade at all, its not necessary anyway...)
Network Connection Error Failed to connect to the internet or previous installation failed.
DVD Read Error Bad burn/media or no cIOS (like IOS 249).
DVD Read Error Bad burn/media or most likely incorrect IOS.
DVD Read Error Bad burn/media or out of date IOS.
DVD Read Error Bad burn/media or out of date IOS. May not be compatible with certain versions of backup launchers (new revs should fix this).
DVD Read Error Bad burn/media or out of date IOS. Possibly a computer issue.
Q. If it is a computer issue, how do I fix it?
A. First, make sure the type of media you're using is compatible with the Wii and/or your computer's DVD Burner. Make sure you are using DVD-R discs, seeing as they are most compatible. Verbatim DVD-R discs burned at 4x work perfectly.
IOS Installation Error Most likely using an old or incorrect IOS, missing an IOS, or the IOS you're trying to install cannot be installed on top of another.
Q. How do I fix this error?
A. Fix it by installing a newer IOS 249 than the one you already have (if you don't have it, try installing it). If you still get this error, fix it the same way as Error 2011.
Wad Install Error Most likely missing trucha sign if you downgraded. Other issues are Out of date IOS or bad/incorrect wad. Memory might be full.
Wad Install Error Most likely incorrect format or corrupt SD card. Memory might be full.
Wad Install Error Most likely have cIOS 37 (or other outdated/incorrect IOS) still installed. Memory might be full. Wad may be corrupt (patched/injected incorrectly).
Q. How do I fix this Error?
A. Fix it by uninstalling IOS249 (use AnyTitleDeleter) if you have it installed. Try using Custom Wad Manager, as some cIOS may be incompatible with the normal Wad Manager. Try a different wad.
Corrupt IOS Most likely caused by using incorrect or bad IOS/wad installations. Fix it the same way as Error 2011.
Update error through waninkoko's 4.1 firmware updater. Caused if ios60 patched was not previously installed.
1048, 1053 & 1101:
DVD Read Error Bad burn/media or incorrect cios/neogamma version. If you are laready using Verbatim DVD-r burned at 4x, try switching to neogammar6 and cios36rev10 (will not work for new wiis/this has worked only for LU39 models). Also this error will persist on newer wiis, meaning that they have the new D3-2 chip which cannot read backups at all. Only option for them is USB loading.
Installation Error Most likely installed incorrect or out of date IOS.
Q. I can't install any IOS, I keep getting an error. How do I fix this?(FIX for errors 1017, 1035,2011)
A. You can use the Trucha Bug Restorer to patch the ios files that are essential for homebrew.