How to fix the bthmodem.sys blue screen (BSOD) in Windows

bthmodem.sys is the Bluetooth Modem Communications Driver, a file that comes with Windows from Microsoft. When a stop screen names it, Windows was running that driver when it crashed, which does not always mean the file itself is at fault. Check first whether Driver Verifier is switched on, then update the Bluetooth driver.

Facts checked on 16 October 2026. Steps written for Windows 11 (25H2 and 26H2) and Windows 10 22H2.

What bthmodem.sys is and why a blue screen names it

bthmodem.sys is the Windows kernel driver for Bluetooth modem communication. Windows lists its service as BTHMODEM, the Autoruns tool shows it as Bluetooth Modem Communications Driver from Microsoft Corporation, and the file sits in C:\Windows\System32\drivers. It is installed with Windows, so you did not add it yourself.

A kernel driver runs inside Windows, so one mistake nearby stops the whole PC. The file named on the stop screen is the one Windows was running at that moment, not always the one that made the mistake. In a Microsoft Q&A thread, an advisor wrote that bthmodem.sys is a Windows component and not the cause, and the crash dump listed a different driver, fltsrv.sys from the Acronis backup software.

Why bthmodem.sys appears in a crash: the causes, in the order to check

No source we read counts how often each cause happens, so this order is by cost: the quickest tests first, and the ones that remove software or roll Windows back last. The Microsoft Q&A reports give the first three.

How to fix the bthmodem.sys blue screen

Most readers start with Fix 1 if they ever ran Driver Verifier, and with Fix 2 if not. Fix 3 finds a program that shares the crash, Fix 4 checks the service, and Fixes 5 to 7 repair Windows itself. Do them in order and restart after each.

Fix 1. Turn off Driver Verifier if it is running

5 minutesLow riskThe stop code is DRIVER_VERIFIER_DETECTED_VIOLATION, or you or a technician ran Driver Verifier on this PC.

Driver Verifier is a Microsoft tool that tests drivers hard and stops Windows on the first violation. In the Microsoft Q&A report the user had switched it on and bthmodem.sys was named almost at once after sign-in. Microsoft documents verifier /reset as the command that turns it off.

1. Right-click Start and select Terminal (Admin) (on Windows 10: Windows PowerShell (Admin)), then select Yes.
2. Type this command and press Enter. It shows the current Driver Verifier settings.

   verifier /querysettings

3. Type this command and press Enter. It clears all Driver Verifier settings.

   verifier /reset

4. Restart the PC and use it normally for a day.

Fix 2. Update the Bluetooth driver

10 to 20 minutesLow riskDriver Verifier is off, and the Bluetooth adapter's driver is old or your PC maker has a newer one.

Outdated, damaged or mismatched drivers can make Windows stop while a Bluetooth driver is loaded. bthmodem.sys itself comes with Windows, so two routes replace the Bluetooth drivers around it: your PC maker's package and Windows Update.

1. Open your PC maker's support page, enter your model and download the newest Bluetooth driver, then run its setup.
2. Right-click Start, select Device Manager, expand Bluetooth, right-click your adapter, select Properties and open the Driver tab. Note the Driver Date and Driver Version.
3. Open Settings > Windows Update > Advanced options > Optional updates (on Windows 10: Settings > Update & Security > Windows Update > View optional updates).
4. Open Driver updates, tick any Bluetooth entry and select Download & install.
5. Restart the PC.

Every way to update, roll back or reinstall a driver, with screenshots: Update, roll back or reinstall a driver

Fix 3. Update or remove the program that shares the crash

15 to 30 minutesLow riskYou use a backup, imaging, security or VPN program, or installed something shortly before the first crash.

A crash names the file Windows was running, and a different driver can be the one that failed. In the Microsoft Q&A report the dump listed one third party driver, fltsrv.sys from Acronis, and the advisor told the user to update or uninstall that product.

1. Open Settings > Apps > Installed apps and sort by Install date (on Windows 10: Settings > Apps > Apps & features, Sort by: Install date).
2. Look for backup, disk imaging, security, VPN or virtual device programs installed or updated before the first crash.
3. Update each one to its latest version from its maker, restart and use the PC for a day.
4. If the crash returns, uninstall the program with its maker's removal tool or with Uninstall a program or app in Windows, then restart.
5. If you cannot tell which program it is, find it with How to perform a clean boot in Windows.

Fix 4. Set the BTHMODEM service back to manual start

5 minutesLow riskA tweak tool, script or manual change altered Windows services, or the start type below looks wrong.

bthmodem.sys loads through the BTHMODEM service. The command sets the service to start on demand, which is the manual start type, so Windows starts it only when a Bluetooth modem needs it. We could not confirm Microsoft's default for this service from a Microsoft page, so read the current value first.

1. Click Start, type cmd, right-click Command Prompt and select Run as administrator.
2. Read the current start type. Look at the START_TYPE line.

   sc qc BTHMODEM

3. Set the start type to manual. Keep the space after the equals sign.

   sc config BTHMODEM start= demand

4. Restart the PC.

Fix 5. Repair damaged Windows system files

20 to 30 minutesNo riskThe fixes above did not help, SFC has never run on this PC, or you see messages about a corrupted bthmodem.sys.

bthmodem.sys is a Windows file, so System File Checker can compare it with the stored copy and replace it if it is damaged. DISM repairs the component store that SFC copies from.

Run the two tools in this order in an administrator window. Step by step with screenshots: Run DISM and SFC to repair Windows system files

In Terminal (Admin) or Command Prompt (Admin), one after the other:

sfc /scannow
DISM /Online /Cleanup-Image /RestoreHealth
sfc /scannow

Restart after the second scan. If SFC reports that it repaired files, use the PC for a day before you judge the result.

Fix 6. Check the file's location and scan for malware

20 to 60 minutesNo riskYou see a second copy of the file, strange behaviour besides the crash, or you want to rule out malware.

Malware can replace or imitate a driver file. The Windows driver sits in System32, so a copy somewhere else is not it, and a full scan checks the rest of the PC.

1. Open File Explorer and go to C:\Windows\System32\drivers. Find bthmodem.sys.
2. Right-click it, select Properties and open the Details tab. Check that the file description and copyright match a Microsoft file.
3. If you find a file with this name in your user folder, Downloads or Temp, do not run it. Scan it as part of Step 4.
4. Open Windows Security > Virus & threat protection, select Scan options > Full scan and select Scan now.
5. If you use another security program, run its full scan too, then restart.

Every step with screenshots: How to scan for malware with Microsoft Defender

Fix 7. Go back to a restore point before the first crash

20 to 40 minutesRead the warningThe crashes began on a known day after an update, driver or program, and a restore point from before it exists.

System Restore returns Windows files, drivers and settings to an earlier point. It helps when a change you made, not the Bluetooth hardware, caused the crash.

1. Press Win + R, type SystemPropertiesProtection and press Enter.
2. On the System Protection tab, select System Restore.
3. Select a restore point dated before the first crash, then select Next and Finish.
4. Wait for the restart, then use the PC for a day.

If Windows does not start, begin from Start Windows or a Mac in Safe Mode and choose System Restore in the advanced options. Every step with screenshots: Undo recent changes with System Restore

Still crashing: what to read, test and send to support

Find out what Windows recorded. Open Event Viewer > Windows Logs > System and look at the minutes before each crash. Windows also writes one .dmp file per crash to C:\Windows\Minidump. A tool that only shows the file at the top of the dump names bthmodem.sys but cannot show the whole stack, as an advisor noted in the Microsoft Q&A report.

• Zip the three newest .dmp files from C:\Windows\Minidump.
• Note your Windows version from Settings > System > About.
• Note the Bluetooth adapter's Driver Date and Driver Version from Device Manager.
• Note the stop codes you saw. Many different codes point at memory: run How to test your RAM with Windows Memory Diagnostic.

To test the Bluetooth hardware, open Device Manager, right-click the Bluetooth adapter and select Disable device for a few days. If the crashes stop, the adapter or its driver is involved. Turn it on again later and use a USB Bluetooth adapter meanwhile.

How to keep the bthmodem.sys blue screen from coming back

Windows 10 left support on 14 October 2025. A PC that can run Windows 11 gets Bluetooth and Windows fixes through Windows Update for longer.

Frequently asked questions

What is bthmodem.sys?

bthmodem.sys is the Windows driver for Bluetooth modem communication. Autoruns lists it as the Bluetooth Modem Communications Driver from Microsoft Corporation, and its service is named BTHMODEM. The file is C:\Windows\System32\drivers\bthmodem.sys and comes with Windows, not with a Bluetooth adapter or an app. The same path is what people search for when they ask about the full file name. A copy anywhere else is not the Windows driver.

Is bthmodem.sys a virus?

The file in C:\Windows\System32\drivers is a Microsoft Windows component, not a virus. A blue screen alone is not a sign of malware. A file with this name in your user folder, Downloads or Temp does not belong to Windows. Do not run it, and scan the PC with Microsoft Defender or your security program (Fix 6). Windows Security then reports anything it finds.

Is bthmodem.sys really the cause of my blue screen?

Not always. The stop screen names the file Windows was running when it stopped, and the real fault can be another driver. In the Microsoft Q&A report, two advisors said bthmodem.sys is part of Windows and not the cause, and one named a backup program's driver, fltsrv.sys. The user wrote that the crash came back after removing it. So treat the name as a clue, and test Driver Verifier, the Bluetooth driver and other programs in order.

What does bthmodem.sys not verified mean?

It is a label from the Autoruns tool, not a Windows error. A 2023 Microsoft Q&A report shows Autoruns marking BTHMODEM red and Not Verified, with Microsoft Corporation as publisher, when Windows said a driver blocked Kernel-mode Hardware-enforced Stack Protection. The only reply told the user to update drivers from the PC maker, and the user had already done that. We found no confirmed fix. Keep Windows updated and do not turn protections off.

Is bthmodem.sys corrupted, and how do I repair it?

Only a scan can tell. Run System File Checker with sfc /scannow, then DISM with the RestoreHealth option, then SFC again (Fix 5). SFC compares Windows files with a stored copy and replaces damaged ones, so you never download the file yourself. If SFC says it cannot repair everything, run the DISM line again before SFC, and read the CBS log only if support asks for it.

Can I delete or disable bthmodem.sys?

Do not delete it. It is a protected Windows file, a deleted copy can be restored by SFC, and removing it can cause new errors. Setting the BTHMODEM service to disabled is also not a repair, and we found no source that explains what else it would affect. Use the manual start type from Fix 4 or the fixes in order. If you need a stable PC today, test with the Bluetooth adapter disabled in Device Manager.

What does DRIVER_VERIFIER_DETECTED_VIOLATION mean?

Microsoft calls it the general bug check for fatal errors found by Driver Verifier. Driver Verifier is a tool that tests drivers and stops Windows when one breaks a rule. If this code appears, Driver Verifier is on, and the file named is the driver it caught, which in the Q&A report was bthmodem.sys together with another third party driver. Turn it off with verifier /reset in an administrator window (Fix 1).

Will turning Bluetooth off stop the blue screen?

It can, as a test. Open Device Manager, right-click the Bluetooth adapter and select Disable device. If the crashes stop for a few days, the adapter or its driver is involved, and a newer driver from your PC maker is the next step. We could not confirm whether bthmodem.sys still loads with the adapter disabled, so a crash that continues does not clear the file. Turn the adapter on again when you finish testing.

Does this affect Windows 11 and Windows 10?

Yes, both. The Microsoft Q&A report about the crash is from Windows 10 in 2019, and the not verified report is from Windows 11 in 2023. The fixes and menu names are the same, with the paths given for each. Windows 10 left support on 14 October 2025, so check that Windows Update still offers your PC driver updates, or plan the move to Windows 11.