CrashWhyPC randomly restarts with no blue screen: what Kernel-Power Event 41 means
A restart with no blue screen almost always leaves Kernel-Power Event 41 in the System log. Two values inside it — BugcheckCode and PowerButtonTimestamp — tell you whether it was a Stop error you never saw, the power button, or the PC losing power.
What Event 41 is
Every time Windows starts, it checks whether it was shut down cleanly. If not, it logs Event 41 (source Microsoft-Windows-Kernel-Power, level Critical): "The system has rebooted without cleanly shutting down first." By itself it only says that something unexpected happened. The values on its Details tab say what.
Read the two values
- Open Event Viewer (Win + R,
eventvwr.msc) and go to Windows Logs → System. - Use Filter Current Log… with event ID
41and open the entry from the time of the restart. - On the Details tab, read
BugcheckCodeandPowerButtonTimestamp. - Match them to the table below.
| Values in Event 41 | What happened | What to do |
|---|---|---|
BugcheckCode is not 0 | A Stop error (blue screen). Windows restarted before you could see it. | Convert the code to hex (159 → 0x9F) and look it up in the Bug Check Code Reference. |
PowerButtonTimestamp is not 0 | Someone pressed and held the power button. | If the PC was frozen first, look into the freeze, not the restart. |
| Both are 0 | Windows could not write a code — power was cut, the power supply failed, or the PC hung hard. | Work through the hardware checklist below. |
When everything is 0: the hardware checklist
Microsoft's guidance for this case points at hardware. In order:
- Turn off overclocking and check whether the restarts stop at stock speed.
- Check the memory with a memory tester, and make sure all modules run at the same speed.
- Check the power supply wattage — especially after adding a graphics card, drives or other devices. Power cuts can be prevented with a UPS (battery backup).
- Check for overheating of the CPU, graphics card and other parts.
- Look at what happened just before — Event 6008 gives the time of the unexpected shutdown; check the Application and System logs around it.
One more case: if all values are 0 and you also see Event 46 from volmgr ("Crash dump initialization failed!"), Windows could not prepare a crash dump at startup — check the page file setting. A blue screen could still be the cause; Windows just had nowhere to write it.
See the blue screen next time
To keep the Stop error on screen instead of restarting at once, open System Properties → Advanced → Startup and Recovery → Settings and clear Automatically restart.
Does Kernel-Power Event 41 mean my power supply is broken?
Not by itself. Event 41 only says Windows did not shut down cleanly. A non-zero bug check code points to a Stop error instead; only when both values are 0 does it point to power or other hardware.
Why does my PC restart with no error message at all?
If power drops or the PC hangs hard, Windows has no time to show or save an error. The only trace is Event 41 with zeros and Event 6008 at the next start.
Sources
Official documentation, checked 2026-10-16.
CrashWhy reads these Windows logs for you and explains what happened in plain English — free for Windows.