How to fix Error 402 on Windows 11

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Troubleshooting Guide: Error 402 – “The Process Is Already in Background Processing Mode”

Why This Error Happens

Error 402 typically occurs when a process attempts to switch to background processing mode using SetPriorityClass() while it is already flagged with the PROCESS_MODE_BACKGROUND_BEGIN state in Windows. This usually happens due to a conflicting application instance, a stuck process thread, or a scheduling task that redundantly calls the background mode API without checking the current process state. Corrupted process handles or improperly terminated background tasks can also leave the system believing a process is still in this mode even after the original instance has closed.

Step-by-Step Resolution Guide

  1. Open Task Manager and End Conflicting Processes
    Press Ctrl + Shift + Esc, locate the application throwing Error 402, right-click it, and select End Task. Also check for duplicate instances of the same executable running simultaneously.

  2. Clear Stuck Background Process States via PowerShell
    Open PowerShell as Administrator and run:

   Get-Process -Name "<ProcessName>" | Stop-Process -Force

Replace <ProcessName> with the actual executable name (without .exe) to forcibly reset its state.

  1. Reset Background App Permissions
    Navigate to Settings > Apps > Installed Apps, find the affected application, click the three-dot menu, select Advanced Options, and toggle Background apps permissions to “Let this app run in the background” off and back on.

  2. Check and Repair Corrupted System Files
    Open Command Prompt as Administrator and run:

   sfc /scannow

Followed by:

   DISM /Online /Cleanup-Image /RestoreHealth

This repairs corrupted system files that may interfere with process priority management.

  1. Disable Background Task Scheduling Conflicts
    Open Task Scheduler (taskschd.msc), navigate to Task Scheduler Library, and check for duplicate or conflicting scheduled tasks tied to the affected application. Disable any redundant entries.

Alternative or Verification Steps

  • Verify the fix: Reopen the application and monitor it in Task Manager’s Details tab—confirm only one instance is running and no error is thrown when switching between foreground/background states.
  • Alternative fix: If the error persists, perform a clean boot (msconfig > Services > Hide all Microsoft services > Disable all) to identify third-party software conflicts causing the duplicate background mode trigger.