ERROR_PNP_REBOOT_REQUIRED - 638 (0x27E)
Device will not start without a reboot.
Updated: Feb 21, 2026
Technical Meaning
The error code ERROR_PNP_REBOOT_REQUIRED indicates that a device or system component requires a reboot to function correctly. This typically occurs when the system detects an issue with a hardware device or driver that cannot be resolved without restarting the system.
Error Details
This error is returned by the Windows Native API, specifically in scenarios where a device's state changes such that it can no longer operate properly until the system is rebooted. The exact nature of the issue may vary and could involve driver updates, hardware configuration changes, or other factors that necessitate a restart.
Usage Context
This error code is commonly encountered during device installation, removal, or when dealing with device drivers. It can also appear in scenarios where the system detects an inconsistency between the current state of the device and its expected operational parameters.
Developer Interpretation
When this error is returned, it signifies that a reboot is required for the system to recognize changes made to hardware or driver configurations. Developers should ensure that their applications handle such errors gracefully by informing users about the need for a system restart and possibly providing instructions on how to proceed.
Related Errors
ERROR_DEV_NOT_EXIST(21)ERROR_DEVICE_REMOVED(14)ERROR_DRIVER_FAILED_TO_LOAD(105)
FAQ
Q: What does the error code 638 mean?
A: The error code ERROR_PNP_REBOOT_REQUIRED indicates that a device or system component requires a reboot to function correctly.
Q: How can I handle this error in my application?
A: You should inform users about the need for a system restart and provide instructions on how to proceed. Ensure your application handles such errors gracefully by providing appropriate user feedback.
Summary
The ERROR_PNP_REBOOT_REQUIRED error code is specific to scenarios where device or driver changes require a reboot. Developers should handle this error by informing users about the need for a system restart and ensuring that their applications can manage such situations gracefully.