In previous Windows versions if you had problems with Windows Update, the first place to look for detailed information was C:\Windows\WindowsUpdate.log file.
In Windows 10 v1607 WindowsUpdate.log file doesn't log any information, instead logging has been moved to System log in Event Viewer.
WindowsUpdate.log now says:
Windows Update logs are now generated using ETW (Event Tracing for Windows).
Please run the Get-WindowsUpdateLog PowerShell command to convert ETW traces into a readable WindowsUpdate.log.
For more information, please visit http://go.microsoft.com/fwlink/?LinkId=518345