This tool is for v5.5.1-v5.5.2 only (because of the HBL loader). OTP and SEEPROM are required, so it is only for previously hacked consoles with backup of those files. (If you installed redNAND before you should be able to dump those files from your SD)
(If you don't have OTP you can take the OTP from someone else because the USB key is the same).

This tool is very experimental, USE AT YOUR OWN RISK.
This tool is based on WFS File Injector.
Credit for @FIX94 for the Haxchi and for @dimok WFS Block Injector for the inspiration.

Instructions: (READ FIRST)

Preparing the USB

1. It is recommended to use a clean USB and format it for this process. The installer is expermintal and may corrupt the file system.
2. Buy and install one of the supported DS VC games, and move it to the usb.

Installing
Choose one of the following methods:

Method 1: Direct install to the USB (faster but more risky)

1. Connect the USB to your PC, and find out the drive index:
   Open PowerShell (WinKey + R, enter powershell)
   Run the command

   Get-WmiObject Win32_DiskDrive

   Find the DeviceID for your USB (Example: \.\PHYSICALDRIVE3)
2. Open command line with admin privileges (Start Menu -> Search for "Command Prompt" -> Right click wnd "Run as Administrator")
3. Go to the directory with the tool:
   

   cd <where you extracted the files from the zip>

4. Run the installer: (Don't forget to replace \.\PHYSICALDRIVE3 with the correct device)
   

   haxchi-pc-installer --image \\.\PHYSICALDRIVE3 --otp otp.bin --seeprom seeprom.bin

   And follow the instructions.

Method 2: Install on an image (safer)

1. Dump an image of the USB device with tool like Win32DiskImager.
2. It is recommended to backup the image.
3. Open ccommand line (WinKey + R, enter cmd)
4. Go to the directory with the tool:
   cd <where you extracted the files from the zip>
5. Run the installer:
   

   haxchi-pc-installer --image <dumped image file> --otp otp.bin --seeprom seeprom.bin

   And follow the instructions.
6. Flash the image back to the USB.

Finishing
Now just connect the USB back to the Wii U. If you run the game HBL should be opened instead.
Now with HBL access it is recommended to move the game back to the NAND and reinstall haxchi again with the regular Wii U installer.


Download (Source)

 

[VinsCool]

Oh my gosh this is fantastic!

Thank you very much for the tools!

 

[OkazakiTheOtaku]

Woah, nice. Great job! This is awesome for people that are on 5.5.2.

inb4 Nintendo patches IOSU with 5.5.3

 

[krueger96]

This is great, thanks

 

[ruiner9]

Success! That was a breeze. Thanks guys, I can stop kicking myself for forgetting to set up my DNS blockers after changing my SSID now.

 

[Blop]

Superb ! But noob question : can it be used if actual sysnand differ from backuped rednand due to factory reset done in the meantime ?

 

[rockleeAce]

Anyone have the OTP and Seeprom files?

 

[Corredor]

Anyone have the OTP and Seeprom files?

You need the SEEPROM dump of your console. You can't simply use the SEEPROM of another console.

 

[EyeKey]

Superb ! But noob question : can it be used if actual sysnand differ from backuped rednand due to factory reset done in the meantime ?

The seeprom usb seed is increased by one every factory reset, so you will need to edit it.

 

[Corredor]

I'd like to know if the Wii U USB key seeds share some common bytes. Maybe we don't need the SEEPROM dump. It would be very interesting if we could compare some samples of the Wii U USB key seeds (without the first 4 bytes).

 

[bseverson34556]

I have to admit I am a little bit stuck on this one. Been a while since I did anything with the Wii U but back during my original mod I dumped with Rednand. That being said I have the full files of mlc.full, slc.full and slccmpt.full nut for some reason my otp.bin and seeprom.bin are both 0 bytes and show nothing. My Wii U ended up getting updated since I forgot to set my DNS last time I had to change drives. I have Mocha on it but naturally have no access to the HBL anymore. Did I miss a step on the bin files somewhere? If so I guess I'll have to wait for a different fix.

 

[Zeecor]

Can I dump OTP and SEEPROM with a hardmod?

 

[THATISRIGHT]

Oh lordy, I am really a noob, what is OTP? And SEEDROM?

 

[nl255]

Success! That was a breeze. Thanks guys, I can stop kicking myself for forgetting to set up my DNS blockers after changing my SSID now.

In that case you probably want to remove the update folder as the next update will likely patch the iosu updates as well.

 

[soterman]

I do not have seeprom

 

[PagaN]

Buy and install one of the supported DS VC games

 

[HtheB]

What exactly does this do? I'm not following this...
If you're WiiU is already hacked, then why would you need to install it again?

 

[JustWantsToPlayGames]

"only for already hacked consoles"

Dammit!

 

[EyeKey]

I have to admit I am a little bit stuck on this one. Been a while since I did anything with the Wii U but back during my original mod I dumped with Rednand. That being said I have the full files of mlc.full, slc.full and slccmpt.full nut for some reason my otp.bin and seeprom.bin are both 0 bytes and show nothing. My Wii U ended up getting updated since I forgot to set my DNS last time I had to change drives. I have Mocha on it but naturally have no access to the HBL anymore. Did I miss a step on the bin files somewhere? If so I guess I'll have to wait for a different fix.

redNAND initialize the otp and seeprom only if needed, so if you didn't use the redNAND sadly they won't be initialized.

Can I dump OTP and SEEPROM with a hardmod?

No

Oh lordy, I am really a noob, what is OTP? And SEEDROM?

Chunk of bytes with encryption keys and etc that can be only accessed from the secure cpu. Could be acquired on 5.5.1 with iosuhax.

What exactly does this do? I'm not following this...
If you're WiiU is already hacked, then why would you need to install it again?

Previously hacked Wii U. If your console is on 5.5.2 without haxchi but you still have a backup of your seeprom. (Which can't be acquired on 5.5.2)
Some people didn't install haxchi at all but used redNAND from the browser, so they have seeprom now.

 

[Deleted User]

Alright, disclaimer to those who plan to install damn CBHC after doing this: MOVE THE DAMN GAME TO NAND.
If you don't then don't come crying that your Wii U fails to boot.