Full Fix: Windows Defender won’t do a quick scan on Windows 10, 8.1, 7

By: Madeleine Dean
6 minute read

Running an antivirus program it’s essential for your system’s security. Windows 10 comes with a built-in antivirus, Windows Defender, that can protect your system against a variety of malware and related threats.

Microsoft’s antivirus program can perform three types of scans: quick, full and custom. Getting the antivirus to scan your computer is pretty simple, all you have to do is check one of the three options and wait for the scan to complete. Unfortunately, recent user reports have revealed that Windows Defender won’t do a quick scan due to an incorrect group or resource state.

Users are complaining Windows Defender won’t do a quick scan

Windows Defender is a solid antivirus, but sometimes Windows Defender won’t be able to perform a quick scan. This can be a problem, and speaking of Windows Defender, here are some similar issues that users reported:

  • Windows defender unable to scan, won’t scan – These are some relatively common problems with Windows Defender, but you can fix them using one of our solutions.
  • Your PC couldn’t be scanned Windows Defender – This is another problem that can appear with Windows Defender. If you encounter it, be sure to check if you don’t have a third-party antivirus running in the background.
  • Windows Defender will not complete scan – Sometimes Windows Defender is unable to complete the scan. If this happens, be sure to check the exclusions list and remove any suspicious exclusions.
  • Windows Defender not scanning Windows 10 – If Windows Defender isn’t scanning, the problem might be the missing updates. Simply update Windows 10 to the latest version and check if that helps.

Solution 1 – Remove third-party antivirus

Apparently, this error message is a temporary bug that is sometimes accompanied by error code 0x8007139F. Restarting and manually updating Windows Defender should be enough to fix this issue.

If this simple action doesn’t solve the problem, make sure you are not running another antivirus program at the same time. If you do, uninstall it, and keep Windows Defender. If you previously had a different antivirus, and you’ve recently installed Windows Defender, it’s also possible that remnants of your previous security program are still present. In this case, you need to completely remove all the traces of your previous antivirus.

You can use specific antivirus removal tools depending on the antimalware software you used. Here’s a list with the removal tools for the most common antivirus programs:

Run the uninstall tool, restart your computer, go to Windows Defender and launch a quick scan.

We also recommend you to download this tool to scan and fix various PC problems, such as file loss, malware and hardware failure. It will also optimize your PC for maximum performance.


Solution 2 – Check the exclusions list

If Windows Defender won’t do a quick scan, the problem might be your exclusions list. According to users, sometimes a malware can add an entire drive to the exclusions list in order to prevent Windows from finding it.

However, you can fix the problem simply by checking your exclusions list. To do that, follow these steps:

  1. Press Windows Key + I to open the Settings app.
  2. When Settings app opens, go to Update & Security section.
    Windows Defender will not complete scan
  3. From the menu on the left select Windows Security. In the right pane click Open Windows Defender Security Center.
    Windows Defender will not complete scan
  4. Select Virus & threat protection.
    Windows defender unable to scan
  5. Now select Virus & threat protection settings.
    Your PC couldn’t be scanned Windows Defender
  6. Scroll down to the Exclusions section and click Add or remove exclusions.
    Windows Defender will not complete scan
  7. If your system drive is on the list, be sure to remove it. You might also have to remove other exclusions from the list.

After doing that, the problem should be completely resolved.


Solution 3 – Change the power options

According to users, if Windows Defender won’t perform a quick scan, the problem might be your power settings. To do that, just follow these steps:

  1. Press Windows Key + S and enter power settings. Select Power & sleep settings from the menu.
    Windows defender won't scan
  2. When Settings app opens, click Additional power settings in the Related settings category.
    Your PC couldn’t be scanned Windows Defender
  3. Now locate your current power plan and click Change plan settings next to it.
    Windows defender unable to scan
  4. Set Turn off the display and Put the computer to sleep options to Never. Click Save changes.
    Your PC couldn’t be scanned Windows Defender

After doing that, check if the problem is resolved. This sounds like a strange solution, but several users reported that it works, so you might want to try it out.


Solution 4 – Install the latest updates

In some cases, you might be able to fix this problem simply by installing the latest updates. Microsoft is working hard to fix Windows 10 bugs and issues, and sometimes a Windows Update might fix your problems.

By default, Windows 10 automatically downloads and installs the updates, but sometimes you can miss an update. However, you can check for updates at any time manually by doing the following:

  1. Open the Settings app and go to Update & Security section.
  2. Now click Check for updates button in the right pane.

If any updates are available, they will be downloaded in the background and installed as soon as you restart your PC. Once your PC restarts, check if the problem is still there.


Solution 5 – Perform SFC and DISM scans

Windows Defender is a core component of Windows 10, and if you can’t perform a quick scan, the issue might be file corruption. Your system files can get corrupted, and that will cause this issue to appear.

However, you might be able to fix file corruption issues by performing SFC and DISM scans. To do that, follow these steps:

  1. Press Windows Key + X to open Win + X menu and choose Command Prompt (Admin). Alternatively, you can also use PowerShell (Admin).
    Your PC couldn’t be scanned Windows Defender
  2. When Command Prompt opens, enter sfc /scannow and press Enter.
    Windows Defender will not complete scan
  3. The SFC scan will now start. The scan can take about 15 minutes, so don’t interrupt it.

Once the scan is finished, check if the problem is still there. If the issue is still present, or if you’re unable to run SFC scan, you might have to use DISM scan instead. To do that, follow these steps:

  1. Start Command Prompt as administrator.
  2. Now run DISM /Online /Cleanup-Image /RestoreHealth command.
    Windows Defender not scanning Windows 10
  3. DISM scan will now start. The scan can take about 20 minutes, sometimes more, so don’t interfere with it.

Once the DISM scan is finished, check if the problem is still there. If you want, you can repeat SFC scan once again and all the corrupted files should be repaired.


Solution 6 – Create a new user account

According to users, sometimes your user account might be damaged, and that can cause issues with Windows Defender to appear. To fix this problem, it’s advised to create a new user account and check if the problem appears on a new account.

To do that, just follow these simple steps:

  1. Open the Settings app and navigate to the Accounts section.
    Windows Defender not scanning Windows 10
  2. In the left pane, select Family & other people. Now choose Add someone else to this PC.
    Windows defender unable to scan
  3. Choose I don’t have this person’s sign-in information.
    Your PC couldn’t be scanned Windows Defender
  4. Select Add a user without a Microsoft account.
    Windows Defender will not complete scan
  5. Enter the username for the new account and click Next.
    Windows Defender not scanning Windows 10

After creating a new user account, switch to it and check if the problem still appears. If not, you’ll need to move your personal files to a new account and start using it instead of your old one.


Solution 7 – Perform a System Restore

If Windows Defender won’t perform a quick scan, you might be able to solve the problem by performing a System Restore. To do that, follow these steps:

  1. Press Windows Key + S and enter system restore. Select Create a restore point from the menu.
    Windows Defender will not complete scan
  2. System Properties window will open. Click System Restore button.
    Windows Defender not scanning Windows 10
  3. System Restore will now start. Click Next to proceed.
    Windows defender won't scan
  4. If available, check Show more restore points option. Select the desired restore point and click Next.
    Your PC couldn’t be scanned Windows Defender
  5. Follow the instructions on the screen to complete the restoration process.

Once the restoration process is finished, check if the problem is still there.


Solution 8 – Try a third-party antivirus

Windows defender won't scan

If Windows Defender won’t perform a quick scan, maybe the best option is to switch to a different antivirus software.

There are many great antivirus tools on the market, and if you’re looking for an antivirus software that will provide maximum protection without interfering with your system, you should consider using BullGuard.

Not being able to perform a quick scan in Windows Defender can be a big problem, but we hope that you managed to fix this issue using one of our solutions.


Editor’s Note: This post was originally published in August 2016 and has been since completely revamped and updated for freshness, accuracy, and comprehensiveness.


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