This is to prevent so many threads popping up about common error codes. Post all your error code woes here. Also, people can use this thread to go in-depth in how to resolve their issues if the following explanations aren't clear.

Will be continuously updated.

You might experience these common error codes during Mario Kart Wii-related game play or when trying to access Wi-Fi:

86420: www.nintendo.com/consumer/wfc/en_na/ds/results.jsp?error_code=86420&system=Wii&locale=en_US&action2.x=22&action2.y=15

91010: www.nintendo.com/consumer/wfc/en_na/ds/results.jsp?error_code=91010&system=Wii&locale=en_US&action2.x=28&action2.y=13

20100: www.nintendo.com/consumer/wfc/en_na/ds/results.jsp?error_code=20100&system=Wii&locale=en_US&action2.x=23&action2.y=16

20102: www.nintendo.com/consumer/wfc/en_na/ds/results.jsp?error_code=20102&system=Wii&locale=en_US&action2.x=0&action2.y=0

85020: www.nintendo.com/consumer/wfc/en_na/ds/results.jsp?error_code=85020&system=Wii&locale=en_US

61070: www.nintendo.com/consumer/wfc/en_na/ds/results.jsp?error_code=61070&system=Wii&locale=lang