sfc /scannow is the most popular command to scan for corrupt system files immediately. It will not only scan, but also try to repair or replace corrupt system files with healthy ones. It requires a Windows installation source to copy files from. The system file checker is a universal command and can be used in all Windows operating systems, including Windows 11, Windows 10, Windows 8, Windows 7 and Windows Vista. This command line can perform several functions. We will discuss these in this article.
SFC Switches
The table below lists all the switches which can be used with the SFC command-line tool, and their functions: Today, we are only going to be focusing on the “sfc /scannow” cmdlet as it is the one that quickly and effectively fixes your operating system.
Running Basic SFC Scan
The simplest (and most convenient) method to run the system file checker command is by running the following cmdlet in an elevated Command Prompt window: The cmdlet will then perform its job and attempt to repair any protected files that may have been corrupted. However, that is not always the case, and users may encounter different errors from time to time. Before we discuss these different errors, let us discuss the various outputs of the basic scan and what each of those means.
Outputs of SFC Scan
As you can observe in the image above, the output of the SFC scan states the following: It then also states the location of a CBS.log file which contains the details of the performed scan – we’ll get into that a moment later. Let us now see all the possible outputs of the SFC scan that different users can encounter and what they mean: Apart from this, there are other possible issues that you may encounter while performing the scan.
Why SFC Scan Failed
You may encounter any one of the following scenarios while performing an SFC scan. The table below lists those scenarios along with their possible solutions. Note: The methods to perform these solutions are discussed below. Before we discuss the different methods to run the SFC scan, bypassing any issues, let us look at the log file generated when an SFC scan is executed.
How to Open SFC CBS.Log File
When you perform an SFC scan, the system automatically generates a log file named “CBS.log.” This file contains information on the scan that was executed, which can help you advanced troubleshoot if you encounter an issue with the SFC tool. The CBS.Log file is saved at the following location: You can open this log file using a text editor, such as Notepad, Word, Wordpad, etc. Follow these steps to open the file: The log file will then open in the text editor. Since the CBS.Log file can be lengthy, you can analyze it using the Find function. You can look for keywords in the entire file using the CTRL + F shortcut keys, and then use the following keywords to look for the details on the file that may have been repaired, not repaired, corrupted, etc. Here is a list of the keywords you can use and the respective features you can find. By analyzing the CBS.Log file, you can pinpoint the files which SFC could not repair, and then replace those files manually using the guide given down below.
How to Fix SFC /ScanNow Failed
If you are not able to fix your operating system using the basic approach for running the SFC scan, then there is still plenty you can do to mitigate the problem. Note: The below methods need to be performed using only an administrative account and any commands need to be run using an elevated Command Prompt. Note: The steps given below need to be performed in a methodical order as given. That is it! This method should eliminate any issues you experience while performing the SFC scan in basic mode. Restart the computer once the scan is complete. There are several ways to enable the built-in Administrator account on a Windows computer. Click here to learn more about them. Perform these steps to boot into Safe Mode with Networking – which means you will have access to the internet which is then later required to run the DISM utility. Your computer will now reboot into Safe Mode. Learn other methods to boot into Safe Mode. The DISM tool can be used to prepare, modify, and repair system images. However, you need an active internet connection to download and replace corrupted content from Windows Update, which is why we opted to boot into Safe Mode with internet connectivity. Follow these steps to run the DISM utility: Once this is done successfully, do not close the Command Prompt. However, if you find the SFC utility is still unable to fix missing or corrupted files, there are still several things you can do. To begin, we suggest you analyze the CBS.Log file, as we discussed earlier in this post.
Run Offline SFC ScanNow from WinPE
The offline version of the SFC scan means that you run the scan from the Windows Preinstallation Environment (WinPE). This method can be especially useful if you are unable to boot into Windows. This process requires a Windows installation device (DVD, bootable USB) that has the same OS version as installed. Perform the following steps to attempt and repair any missing or corrupted system files using the SFC scan with WinPE. If this does not work for you either, you can manually replace the corrupted files yourself. Note down the drive letter beneath “Windows Boot Loader” in front of device. Note: Since the drive letters assigned in WinPE are not the same as the default drive letters you see when Windows is booted, these can be different for everyone. Therefore, it is important to determine which drive letter is currently assigned to the boot volume.
Manually Replace Corrupted Files
At this point, you must have already analyzed the VBS.Log file we had discussed earlier. Using the file names determined from there, you can manually replace them with healthy files obtained from another computer. Here is how to do it: That is it! You can now repeat the same process to manually replace any corrupted files.
Scan Other Non-OS Volumes using SFC
It may be possible that you are running more than one operating system on your PC, and not all of them can be in the same drive (usually the C drive). In that case, you must direct the SFC scan to attempt and repair another drive. Furthermore, you can also direct it to scan external drives, such as USB flash drives, SD cards, etc. Here is how to do so: Note: Since SFC can only fix missing and corrupted files, it can only attempt to repair drives with a Windows operating system in it. The scan will now attempt to repair any corrupted or missing files that you selected other than the C drive.
How to Fix “Windows Resource Protection Could Not Start The Repair Service”
It may be possible that you encounter the following error while trying to run an SFC scan on your computer: If so, here are a few things you can do to mitigate this issue:
Start Dependency Service
It may be possible that a dependency service named “Windows Modules Installer (Trusted Installer)” isn’t running on your computer, preventing the scan from happening. In that case, the service needs to be enabled. Learn other methods to enable and disable Windows services.
Disable Turbo Memory
Intel Turbo Memory is a feature that allows NAND memory modules to power up, access programs, and write data on the hard drive much quicker than usual. This feature can be controlled through the system BIOS. If you experience an SFC scan suddenly stops or cannot complete its job, then you must disable Turbo Memory from the BIOS settings. Learn how to access BIOS.
Modify Security Descriptors
A Security Descriptor contains security information that may be associated with a securable object. It may be possible that critical Security Descriptors may have corrupted in the WinSXS folder where critical files are stored. To mitigate this issue, perform the following task:
Other Mitigation Methods
If you encounter the said error, there are other things you can also perform which we have already discussed above in this post. Here is a list of additional steps you can take:
Run Check Disk Utility. Run DISM utility. Run SFC scan in Safe Mode. Replace corrupted files manually.
