Fix TPM_E_BAD_DATASIZE (0x8028002B) on Windows 10/11

You're staring at TPM_E_BAD_DATASIZE (0x8028002B) and wondering why your TPM suddenly hates you. It's frustrating, I get it. But here's the deal: this error almost always means the TPM blob (that encrypted data packet) got corrupted or doesn't match the key it's supposed to. The fix is straightforward—clear the TPM and start fresh.

The Fix: Clear and Reinitialize the TPM

Warning: clearing the TPM wipes BitLocker keys, fingerprint data, and Windows Hello PINs. Make sure you have a BitLocker recovery key saved somewhere—Microsoft account, USB drive, or printed. I've seen a client lose access to a whole encrypted drive because they skipped this. Don't be that person.

Step 1: Back Up What Matters

• Open BitLocker Control Panel (control /name Microsoft.BitLockerDriveEncryption) and back up your recovery key.
• If you don't have BitLocker, you're fine—just clear it.

Step 2: Clear the TPM via Windows Security

1. Press Windows + R, type tpm.msc, hit Enter.
2. In the TPM Management console, look for TPM Manufacturer Information. If the status says The TPM is ready for use or TPM is not initialized, you're in the right place.
3. Right-click Clear TPM in the Actions pane, then click Clear TPM. You'll need to restart—do it when you're ready.
4. After reboot, the TPM will reset. Windows should reinitialize it automatically.

Step 3: If That Fails—Use PowerShell

Sometimes the GUI ghosts you. Open PowerShell as admin and run:

Clear-Tpm

This does the same thing. If it errors out with Tpm not initialized, you might need to turn the TPM off and on in BIOS. More on that in a sec.

Why This Works

The 0x8028002B code means the TPM received a blob whose size doesn't match what it expects. This happens when a Windows update changes the TPM driver, or when a firmware update on the motherboard corrupts the stored blob. Clearing the TPM wipes all blobs and forces Windows to create new, properly sized ones. It's like erasing a blackboard and starting with clean chalk.

Real scenario: Had a client last month whose Dell OptiPlex 7080 started throwing this after a BIOS update. Cleared the TPM, re-set BitLocker, and it's been solid for six weeks.

Less Common Fixes

If clearing the TPM didn't do it, you're in the 10% zone. Try these:

1. Update TPM Driver

Open Device Manager, go to Security devices, right-click Trusted Platform Module 2.0, select Update driver > Browse my computer > Let me pick. Choose the latest driver from the list. Reboot.

2. Reset TPM in BIOS

Reboot, mash F2 or Del to enter BIOS. Look for Security > TPM (sometimes called PTT on Intel or fTPM on AMD). Disable it, save and exit, reboot, go back in, and re-enable it. This physically resets the chip.

3. Check for OS Corruption

Run sfc /scannow and DISM /Online /Cleanup-Image /RestoreHealth from admin command prompt. Corrupted system files can mess with TPM interactions.

Prevention for Next Time

• Always back up BitLocker recovery keys to your Microsoft account before touching BIOS updates.
• Keep TPM firmware updated via your motherboard manufacturer's support page—don't rely on Windows Update for this.
• If you're on a custom-built PC with AMD fTPM, know that Ryzen CPUs had a known issue with fTPM stuttering and blob corruption. Check your motherboard's BIOS changelog for fixes.

That's it. Clear the TPM, write it off, and move on. If you're still stuck after all this, your TPM chip might be physically failing—consider replacing the motherboard or using a discrete TPM module.