Microsoft is breaking things in Windows 10 again. A recent update, KB4511555, has resulted in high CPU usage on many systems. High CPU usage is a common enough bug on Windows 10 but this particular bug is because the update has broken something in Cortana/Windows Search. The good news is there’s a fix for the KB4511555 high CPU usage bug. The bad news is that once applied, you will only be able to use Bing for Windows search and Cortana.
Note: some users who have received the KB4512941 update are also experiencing this bug in which case, the same fix applies.
Fix KB4511555 high CPU usage bug
There are two indicators of this bug; the first is the obvious high CPU usage. You can check CPU usage from the Task Manager. Go to the Processes tab, and sort items by CPU usage. You will find that either Cortana or SearchUI.exe is consuming the most CPU.
The second indicator is the search feature not working on Windows 10. It will either fail to load completely or it will only partially work.
Take preventive measures
If you haven’t downloaded/installed this update, it’s best to skip it until a patched one is out. If you have the option to roll back/uninstall the update, go with that option. If not, use the fix below. The fix requires that you edit the Windows registry so you will need admin rights for this.
Tap the Win+R keyboard shortcut to open the run box. In the run box, enter ‘regedit’. Once you have the registry open, go to the following key.
Here, look for a value called ‘BingSeachEnabled’. Double-click it and set its value to 1. Alternatively, you can just delete this value. Restart your system to apply the change.
Your CPU usage will go back to normal however, web results in Windows Search will start to use Bing and no one really uses Bing. You can try using an app like SearchDeflector to change which search engine Cortana/Windows search uses but it may not work. In order to force Cortana/Windows search to use a different search engine or browser, users make use of certain loopholes which, when discovered, are patched by Microsoft. This means that your current Windows 10 version may not allow you to use SearchDeflector to fix Cortana or Windows Search.
As far as a real fix is concerned, it’s going to have to come from Microsoft. There is no ETA for it but it shouldn’t take more than a month unless something really big is broken.