0XC01D0006 Monitor Serial Number Error Fix

What triggers this error

You're working on a Windows 10 or 11 PC, and suddenly you get a notification or a device manager error: STATUS_MONITOR_INVALID_SERIAL_NUMBER_MONDSC_BLOCK (0XC01D0006). The culprit here is almost always a monitor cable swap—VGA to HDMI, DisplayPort to DVI, or even just plugging a monitor into a different port on your GPU. It can also pop up after a GPU driver update that re-negotiates the DDC/CI (Display Data Channel Command Interface) link. The monitor's EDID contains a serial number block, and Windows is trying to read it over DDC. But the monitor doesn't send it back correctly—either the block is corrupt, missing, or the monitor's firmware doesn't follow the standard.

Root cause

Modern monitors stuff their serial number into a monitor serial number descriptor block inside the EDID (Extended Display Identification Data). Some monitors—cheaper ones, older ones, or ones with buggy firmware—either don't include this block at all, or they include it with garbage data. When Windows checks DDC/CI for the serial number and finds something it can't parse, it throws this error. It's not a hardware failure. It's a shitty EDID implementation on the monitor side.

Fix it in 4 steps

Step 1: Disable DDC/CI in the monitor's OSD (if supported)

This is the fastest fix. Most monitors have a setting in their on-screen display menu called something like "DDC/CI", "Control Sync", or "USB-C Control". Turn it off. This stops Windows from trying to talk to the monitor over DDC, which means it won't try to read the serial number block. No serial number request, no error.

Where to look: Samsung calls it "HDMI CEC" or "DDC/CI" under System. Dell has it under "Others" or "Menu Settings". LG buries it in "General" > "Quick Settings" > "DDC/CI". Check your monitor's manual.

Step 2: Force a fresh EDID read from the GPU driver

If you don't want to touch the monitor settings, you can force the GPU to re-read the EDID. This clears any cached crap.

NVIDIA: Open NVIDIA Control Panel > Display > "Change resolution" > scroll down and click "Customize" > then "Reset to defaults" (or just restart the driver with Win+Ctrl+Shift+B).
AMD: Open Radeon Settings > Display > "Additional Settings" > "HDMI Scaling" > set it to 0% then back to auto. Or restart the driver with Win+Ctrl+Shift+B.
Intel: Open Intel Graphics Command Center > Display > click on the monitor > scroll to "Advanced Display Settings" > hit "Restore Defaults".

After that, unplug and replug the monitor cable. Wait 10 seconds. See if the error comes back.

Step 3: Delete the monitor driver from Device Manager

Sometimes Windows caches a corrupt EDID in the driver store. Here's how to nuke it:

Press Win + X and select Device Manager.
Expand Monitors.
Right-click your monitor (it's usually "Generic PnP Monitor" or the specific model name).
Select Uninstall device. Check the box that says "Delete the driver software for this device" if it appears.
Reboot your machine. Windows will re-detect the monitor and grab a fresh EDID.

This works 80% of the time if the issue is just a corrupt cache.

Step 4: Override the EDID with Custom Resolution Utility (CRU) – advanced

If the error persists, the monitor's EDID is genuinely broken. You can override it with Custom Resolution Utility (CRU). This is a third-party tool but it's the nuclear option.

Download CRU from ToastyX (it's free and safe).
Run it as administrator.
Select your monitor from the dropdown at the top.
In the Monitor Serial Number section, you'll see the corrupt or missing block. Click Delete to remove it.
Click OK and then run restart64.exe (or reboot).

This removes the serial number block entirely. Windows won't see it, won't try to read it, and the error vanishes. Caveat: Some apps (like color calibrators) rely on the serial number to identify the monitor. If you use one, this might cause confusion.

What to check if it still fails

If you've done all 4 steps and the error keeps coming back, it's time to check the hardware:

Cable: Try a different cable. Sometimes a flaky DisplayPort or HDMI cable introduces noise on the DDC line. A shielded cable fixes that.
GPU port: Plug the monitor into a different port on your GPU. If the error goes away, the original port might have a bent pin or a bad solder joint.
Monitor firmware: Check the monitor manufacturer's support page for a firmware update. Dell and LG occasionally release patches that fix EDID bugs. I've seen this fix Dell U-Series and LG 27GN models.
Replace the monitor: If you're on a cheap no-name monitor, the EDID might be hardcoded in a faulty chip. There's no fixing that without a re-write of the monitor's firmware chip, which isn't practical. Swap it out.

One last thing: if you're using a KVM switch or an extended display dock, bypass it. Connect the monitor directly to the GPU. Those devices often mess up DDC communication.