What does HRESULT 0x8031009C (FVE_E_EFI_ONLY) mean?

FVE_E_EFI_ONLY

Read this as a state-machine result

FVE_E_EFI_ONLY is a BitLocker facility HRESULT, not a Win32 filesystem error wrapped by an application. In this case the requested BitLocker feature depends on UEFI services and cannot run on a legacy BIOS boot path.

For FVE_E_EFI_ONLY, note: Hardware-encrypted drives add firmware, storage-driver and drive-security state below the normal BitLocker volume provider. When diagnosing FVE_E_EFI_ONLY, remember: BitLocker can reject the hardware path before conversion starts, and policy may or may not permit a fallback to software encryption.

What the code does not prove

The closest misleading interpretation is FVE_E_FIRMWARE_TYPE_NOT_SUPPORTED, which can cover a broader unsupported firmware configuration for OS-volume enablement. For FVE_E_EFI_ONLY, verify the returning method and state transition before assigning the incident to disk corruption, TPM failure or bad credentials.

Inspect the target, not just the message

1. For FVE_E_EFI_ONLY, record firmware mode, disk partition style, active boot loader, Secure Boot state and the feature being invoked. For FVE_E_EFI_ONLY, keep the full HRESULT and the first method that returned it because later cleanup calls can report a different state.
2. For FVE_E_EFI_ONLY, capture manage-bde -status and the protector inventory for the exact volume GUID, not only the drive letter, because letters can change in WinRE, clusters and deployment environments.
3. Export BitLocker operational events for the FVE_E_EFI_ONLY failure and note the boot session, caller identity and management source; that evidence separates this BitLocker condition from a generic access or storage error.

For FVE_E_EFI_ONLY, note: Firmware, storage drivers and security-band state can change independently. When diagnosing FVE_E_EFI_ONLY, remember: A successful filesystem check does not validate the eDrive management channel.

A low-risk recovery path

• For FVE_E_EFI_ONLY, migrate to a supported UEFI/GPT boot configuration through documented deployment procedures before retrying the feature.
• After correcting the FVE_E_EFI_ONLY prerequisite, refresh protection, conversion and lock state before one controlled retry; a cached UI message is not proof that the FVE_E_EFI_ONLY condition is still active.
• Before a FVE_E_EFI_ONLY remediation deletes protectors, changes firmware mode, resizes partitions or decrypts a production drive, verify that an independent recovery method is available and escrowed in the intended directory or account.

manage-bde -status
powershell -NoProfile -Command "Get-CimInstance -Namespace root/cimv2/security/MicrosoftVolumeEncryption -Class Win32_EncryptableVolume"

Result interpretation for FVE_E_EFI_ONLY

After correction, compare the new conversion, protection and lock state with the original snapshot. A different HRESULT after FVE_E_EFI_ONLY is useful because it means the request crossed this boundary and reached the next prerequisite.

State checks specific to FVE_E_EFI_ONLY

Verification after the change

For FVE_E_EFI_ONLY, success means more than the absence of a dialog. Confirm that the condition represented by FVE_E_EFI_ONLY now matches the intended design, that the protector inventory has not lost an independent recovery route, and that the next reboot or remount can unlock the volume. If the FVE_E_EFI_ONLY request advances to another HRESULT, record both values in order because that transition reveals the next unmet prerequisite.

References

Reference set for FVE_E_EFI_ONLY:

• Microsoft: Encrypted hard drives
• Microsoft: GetHardwareEncryptionStatus method
• Microsoft: BitLocker operations guide
• Microsoft: Configure BitLocker policy

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