Situation:
Unable to find your specific error code. Please search your Wii U error code again, making sure to enter it exactly as it appears.
If you are still unable to locate troubleshooting for your specific error code, below is a list of troubleshooting steps that resolve most home network connection issues:
What to do:

Power cycle your home network.

If your wireless router or access point is unresponsive, power cycling these devices may resolve your connection issue. [How to]

Ensure you are using the correct password for your Wi-Fi network.

If your wireless router or access point is secured with a security key or password, review this password to ensure you have entered it correctly in the Wii U. [How to]

Create a new connection on your Wii U.

Create a new connection on your Wii U. This will ensure you are connecting to the correct Wi-Fi network and the Wi-Fi network is currently visible to your Wii U. [How to]

Check for wireless interference.

Wireless interference can result in a weakened connection between your Wii U and your wireless router or access point. Review your Wi-Fi network’s setup to ensure an optimal wireless environment. [How to]
Still Not Resolved:

Situation:
Unable to find your specific error code. Please search your Wii U error code again, making sure to enter it exactly as it appears.
If you are still unable to locate troubleshooting for your specific error code, below is a list of troubleshooting steps that resolve most home network connection issues:
What to do:

Power cycle your home network.

If your wireless router or access point is unresponsive, power cycling these devices may resolve your connection issue. [How to]

Ensure you are using the correct password for your Wi-Fi network.

If your wireless router or access point is secured with a security key or password, review this password to ensure you have entered it correctly in the Wii U. [How to]

Create a new connection on your Wii U.

Create a new connection on your Wii U. This will ensure you are connecting to the correct Wi-Fi network and the Wi-Fi network is currently visible to your Wii U. [How to]

Check for wireless interference.

Wireless interference can result in a weakened connection between your Wii U and your wireless router or access point. Review your Wi-Fi network’s setup to ensure an optimal wireless environment. [How to]
Still Not Resolved:

Situation: •This error code typically indicates an issue communicating and matchmaking with other players. •This is often caused by network firewalls blocking necessary network traffic. •This can be caused by your network, or the network of the person you are connecting with. If these steps do not resolve your connection issue, have your friend try them as well. What to do: •Power cycle your home network. If you have been able to connect with others before, and this issue only recently started, power cycling your network may allow you to connect with others again. [How to] •Check our network status information. Review our Network Status page and ensure there are no service notifications related to Wii U matchmaking services. •Ensure your Wii U is connected online and try again. Test your Wii U console’s Internet connection by performing a connection test. If the connection test fails, use the error code provided to troubleshoot your Wii U console’s Internet connection. •Manually enter your network IP address and DNS information. Manually entering your network information into the Wii U console's Internet settings may help you resolve this matchmaking issue. [How to] •Place the Wii U into your router's DMZ (demilitarized zone)*. Placing the Wii U in your router's DMZ will allow it to bypass your router's firewall and allow you to connect with others. [How to] *While Nintendo provides this information for our consumers' use, it is up to each consumer to determine what security needs they have for their own networks, and to decide how best to configure their network settings to meet those needs. Still Not Resolved: If the above steps did not resolve the issue, and you continue to experience problems, please click the button below to see which options are available to contact us for further assistance. I hope this helps you out.