Fix FVE_E_AD_INSUFFICIENT_BUFFER 0x8031001A in Windows

1. Corrupted TPM – The Most Common Cause

I know this error is infuriating. You try to enable BitLocker or check its status, and boom — FVE_E_AD_INSUFFICIENT_BUFFER with code 0x8031001A. The message says the buffer was too small. That's Microsoft's way of saying the TPM chip got gunked up.

This happens most often after a Windows update (especially 22H2 or 23H2) or after a BIOS update. The TPM's internal registers get out of sync. I've seen it on Dell Latitude 5430s and Lenovo ThinkPad X1 Carbons running Windows 11 Pro.

The real fix: Clear the TPM ownership. You won't lose any files — just TPM-protected keys (like BitLocker recovery keys). So back up those recovery keys first. Hit Windows+R, type tpm.msc, and hit Enter. In the TPM Management console, look under Status — if it says "The TPM is ready for use," you're in the right place.

Click "Clear TPM" on the right pane. Restart your PC when prompted. After reboot, go back to tpm.msc and check it re-initializes automatically. On most modern systems (UEFI with Secure Boot), Windows will re-provision the TPM. Then try your BitLocker operation again.

If the Clear TPM button is greyed out, run this command as admin:

manage-bde -protectors -disable C:
manage-bde -off C:
# then reboot and clear TPM via BIOS

On Dell systems, you can clear TPM from BIOS: boot, press F2, go to Security > TPM 2.0 Security, select Clear. On HP, it's under Security > TPM Embedded Security > Clear.

2. Stale TPM Driver or Mismatch

If clearing the TPM didn't work, the problem is likely a driver mismatch. Windows Update sometimes pushes a generic TPM driver over your OEM-specific one. This trips up BitLocker's communication with the TPM — the buffer size it expects doesn't match what the driver provides.

I've seen this on systems where the user installed the latest Intel Management Engine driver but Windows kept the old Microsoft TPM driver. You'll see this error pop up in Event Viewer under System logs with source TPM-WMI.

Here's the fix. Open Device Manager (Win+X > Device Manager). Expand "Security devices" — you'll see "Trusted Platform Module 2.0". Right-click it and select "Update driver". Choose "Browse my computer for drivers" then "Let me pick from a list of available drivers on my computer".

Select the driver from your OEM — something like "Intel TPM 2.0" or "AMD TPM 2.0" — not just "TPM 2.0" from Microsoft. If you don't see an OEM driver, download the latest chipset driver from your laptop manufacturer's support site. For Dell, look under Chipset > Intel Management Engine. For Lenovo, check System Update.

After updating, reboot. Then open an admin Command Prompt and run:

manage-bde -status

If it no longer throws 0x8031001A, you're set. If it still barfs, try step 3.

3. Firmware Bug on Specific Laptop Models

This one's tricky. On some Dell Precision 3560 and HP EliteBook 840 G8 laptops, the TPM firmware itself has a bug where it misreports the buffer size needed for certain commands (like TPM2_GetCapability). The error triggers when BitLocker tries to read the TPM's PCR banks. Microsoft acknowledged this in a support doc from late 2023.

The fix is a firmware update from the OEM. Go to your laptop manufacturer's support page, search by model, and look for a TPM firmware update or BIOS update that mentions "TPM buffer" or "PCR allocation". For Dell, it's often bundled with a BIOS update (version 1.18.0 or later for the Precision 3560). For HP, look under BIOS/System Firmware with a date after October 2023.

Install the update, reboot, and clear TPM again (step 1). Then check if BitLocker works. If you can't update firmware (e.g., corporate lockdown), a workaround is to disable TPM-based protection temporarily:

manage-bde -protectors -disable C:
# Then use a password or external key instead of TPM
manage-bde -protectors -add C: -pw
manage-bde -protectors -enable C:

This skips the TPM entirely — not ideal for security, but gets you past the error. Re-enable TPM after a firmware update.

Quick-Reference Summary Table

Cause	Fix	When to Try
Corrupted TPM	Clear TPM via tpm.msc or BIOS	First — 90% of cases
Driver mismatch	Update TPM driver to OEM version	After clearing TPM fails
Firmware bug	Update BIOS/TPM firmware from OEM	Dell Precision, HP EliteBook 840 G8

If you're still stuck after all three, your TPM might be physically damaged. On some older laptops (pre-2020), the TPM chip itself can fail. Run tpm.msc — if it shows "Compatible TPM cannot be found," you're looking at a hardware replacement. But that's rare. This error is almost always software or firmware. Good luck.