Before we get going with solutions to fix the Diagnostic Policy Service high CPU usage, we need to know precisely this service. It is a service that runs in the Windows background to ensure that the PC is working fine. This service is responsible for detecting and troubleshooting issues related to the components of the Windows OS. If your PC suddenly runs into trouble, the Diagnostic Policy Service takes care of it to keep your PC up and running.
Now, it is very unusual for the Diagnostic Policy Service to utilize high CPU resources. But when this happens, it utilizes a good chunk of the performance resources, making it difficult for you to carry out other tasks on your PC.
Can I disable Diagnostic Policy Service?
The Diagnostic Policy Service in Windows 10 is among the essential services that start automatically as your PC boots. Although it starts automatically, you can stop it manually through the Services tool. You can even disable this service if you want. This way, the Diagnostic Policy Service will not start automatically when you boot into Windows.
Now, let us take a look at the methods to fix the issue.
How to Fix Diagnostic Policy Service High CPU Usage?
End Diagnostic Policy Service Task in Task Manager
If you find the Diagnostic Policy Service utilizing high CPU usage, one of the first things to try would be to end the process through Task Manager. Doing so will most probably fix the issue; here’s how:
Step 1: Open the Task Manager by pressing the Ctrl + Shift + Esc keys.

Step 2: In the Task Manager window that opens, make sure you are in the Processes tab. Now, scroll down to the Windows processes section and look for the process named Service Host: Diagnostic Policy Service. Select the service and click on the End Task button.
If this doesn’t stop the process by any chance or the process reappears and continues utilizing high CPU resources, try the next solution.
Run SFC Scan
The SFC Scan in Windows is meant to look for corrupt system files or files with issues and fixes them when found. It is a command-line utility; here are the steps to run the scan:

Step 1: Open Command Prompt with Admin privileges. For this, press Win + S to open the Start menu search panel. Type cmd in the search panel. From the search results, make a right-click on the Command Prompt option, select the Run as administrator option.

Step 2: The Command Prompt window will open. Here, type the following command and press the Enter key: SFC /scannow
The scan will commence and carry out the assigned job. If any file(s) with issues caused the diagnostic policy service to utilize high CPU resources, it would be fixed. Restart your PC and see if the issue is still there.
Run DISM Scan
Another Command Prompt utility, the DISM scan, also fixes your PC’s issues that could be causing the diagnostic policy service to consume high CPU usage.
Step 1: Open Command Prompt in Admin mode, as shown above.

Step 2: In the Command Prompt window, type the command given below and hit the Enter key:
DISM /Online /Cleanup-Image /ScanHealth
The scan may take some time to complete; wait patiently till it over. Once the scan is complete, restart your PC. Was the Diagnostic Policy Service High CPU usage issue fixed?
Update Device Drivers
If your device drivers are not up to date, your PC may face issues like this. Make sure that the drivers are updated; if not, update them.

Step 1: Press the Win + X keys. In the menu that opens, select the Device Manager option.

Step 2: In the Device Manager, you will see a list of devices installed on your PC. Click on a tool to expand the list of drivers associated with the device. Make a right-click on the driver and select the Update Driver option.
If an update is available, you will be prompted about the same. Follow the on-screen instructions to update the driver successfully.
Now, do the same for all the devices you can see in the Device Manager list. It is a time-consuming process, and to skip all the hassle; you can install a Driver Updater software on your PC. This software carry out the driver update process automatically once initiated.
After successfully updating the device drivers, give your PC a restart and check if the Diagnostic Policy Service high CPU usage issue persists.
Update Windows 10
Carrying out a Windows update on your PC can be helpful with issues such as this one. Make sure that Windows is updated to the latest available version. Follow these steps:

Step 1: Open the Settings app in Windows 10. For this, press the Win + I keys. In the Settings app, make a click on the Updates & Security option.

Step 2: A new window will open. Here, make sure that the Windows Update option is selected on the left pane. Then, go to the right pane and click on the Check for updates option. Now, Windows will begin looking for the latest update. See that your PC has an active internet connection. If an update is found, you will have to follow the on-screen instructions to complete the update.
Once the Windows restarts after the update, check for Host Diagnostic Policy Service High CPU usage.
Update BIOS on your PC
BIOS is responsible for running your PC’s motherboard. If the BIOS on your PC is outdated, it may cause a spectrum of issues, including your face. Make sure that the BIOS on your PC is up to date.
For this, you will have to enter the BIOS setup on your PC. Restart your PC and press the key assigned to enter the BIOS setup. Depending on the motherboard manufacturer, it could be F2, F10, F11, F12, or Esc keys.
The BIOS settings vary too among motherboard manufacturers. If you are unable to figure out the process of BIOS update in the BIOS setup, you can also check out the motherboard user manual.
Once the BIOS updates successfully, see if the service host diagnostic policy high CPU usage issue is still there.
Delete the SRUDB.dat File
You could delete the SRUDB.dat file on your PC if none of the above solutions worked for you. Here’s how to do it:

Step 1: Press Win + R keys, and in the Run box that will open, type the following text: %WinDir%\System32\sru

Step 2: Windows File Explorer will open with a list of files. Here, make a right-click on the SRUDB.dat file and select the Delete button.
The SRUDB.dat file will be deleted. Restart your PC now. This will take care of the host diagnostic policy high CPU usage issue.
Closing Words
Even though the above solutions are enough to help you get rid of the diagnostic policy service high CPU issue, otherwise you can carry out a System Restore or even Reset Windows. These will get rid of the high CPU usage issue.