Not turning on the Wii U can kill it
If you've had your Wii U wrapped up in a box in storage, you might want to take it out and power it up. The console is apparently prone to memory corruption, and it may die on you if you let it sit without power for too long.
You can check this by powering up your console and seeing if it loads to the main menu or gives you an error. Sometimes, these error codes are delayed, so you may want to boot up a few games and see if they work fine.
This is a known issue, with many owners reporting seeing the "160-0103" and "160-2155" error codes on forums after leaving the console to collect dust for a while. The error codes identify an issue with the console's eMMC memory - a storage chip containing NAND flash memory and a controller.
Nintendo used chips manufactured by Toshiba, Samsung or Hynix. The Hynix chips are most prone to failure, but that doesn't mean there aren't reports of the Toshiba or Samsung chips failing.
Thankfully, this online database lists eMMC chips from all Wii U models. The general consensus says that the original White Wii U model (WUP-001 as per the database) is the least likely to suffer from this failure.
The fix requires disassembly and soldering. If you are okay with that, you can try Voultar's Wii-U NAND Recovery Kit to see if that fixes the problem. It's worth noting that any mistake here could lead to a potentially bricked console. If you are unsure about the method or lack the necessary tools, don't risk it and seek out a professional.
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