How to Fix ERROR_INTERRUPT_VECTOR_ALREADY_CONNECTED

The ERROR_INTERRUPT_VECTOR_ALREADY_CONNECTED (error code 0x3C1) occurs in Windows when an interrupt vector is already in use by another device or process. Interrupt vectors are used by hardware and software to signal events, and this error typically arises in driver development or system-level programming. So, it’s typically linked to duplicate vector assignment, driver misconfiguration or system restore conflicts.

How do I fix ERROR_INTERRUPT_VECTOR_ALREADY_CONNECTED?

How to fix the error in a coding environment

1. Verify the driver code (coding environment)

• Ensure the driver does not attempt to register an interrupt vector already in use.
• Review the code that allocates interrupt vectors using functions like IoConnectInterruptEx or similar APIs.
• Properly release previously allocated vectors using the IoDisconnectInterrupt function.

2. Use unique vectors (coding environment)

• Assign unique interrupt vectors for devices or processes.
• Use APIs to query available vectors dynamically: STATUS = HalAllocateInterruptVector(...);
• This avoids hardcoding interrupt numbers.

After you perform the changes, also review the driver’s INF file to ensure proper resource assignments and avoid conflicts during installation.

If you can’t identify the issue in your code, use tools like WinDbg to analyze system logs and identify the source of the interrupt conflict. Also, analyze kernel-level logs for details about interrupt allocation failures.

How to fix the error in system usage scenarios

1. Update or reinstall the drivers

1. Press Win + X and select Device Manager.
2. Expand the categories and check if any of the components features a yeloow exclamation mark next to it, indicating an issue.
3. Right-click on the device and select Update driver.
4. Choose Search automatically for updated driver software and follow the prompts.
5. If that doesn’t work, select Uninstall device instead of Update driver in step 3 and restart your PC to allow the system install a default driver.

If the ERROR_INTERRUPT_VECTOR_ALREADY_CONNECTED bug check was triggered after a driver update or after installing new hardware, the problem may be caused by a poorly coded driver or driver corruption. If the solution above doesn’t work, go to the manufacturer’s website and download the right driver for your system. We also recommend installing a driver updater tool that will automatically fix this problem in just a fraction of the time.

2. Check the BIOS firmware or settings

Although less likely, the ERROR_INTERRUPT_VECTOR_ALREADY_CONNECTED may be caused by a wrong BIOS interrupt handling. In this case, we recommend updating your BIOS to the latest version.

We have a complete guide on how to update the BIOS. For advanced users, it’s also possible to configure hardware interrupts from BIOS/UEFI to avoid such conflicts.

3. Perform a Clean Boot

1. Press Win + R, type msconfig, and press Enter.
2. Go to the Services tab and check Hide all Microsoft services.
3. Click Disable all.
4. Go to the Startup tab and click Open Task Manager.
5. Disable all startup items.
6. Close Task Manager and click OK in the System Configuration window.
7. Restart your computer.

After the restart, the system will run with a minimum processes and drivers, allowing you to troubleshoot this error a lot faster.

To prevent the ERROR_INTERRUPT_VECTOR_ALREADY_CONNECTED, avoid hardcoding interrupt numbers in drivers and regularly update firmware and drivers to maintain compatibility.

Using hardware diagnostics tools may also help you identify potential resource conflicts.

If these steps do not resolve the issue, consult Microsoft Developer Network (MSDN) resources or submit a support request for further troubleshooting and information.

We hope that our guide provided sufficient information to help you fix the ERROR_INTERRUPT_VECTOR_ALREADY_CONNECTED bug check. For any suggestions or questions, feel free to access the comments section below.