Cable HDMI connection to TV has stopped working

[Tamrac99]

Configuration:

      Laptop Pavillion 15-cs0013na 

       TV: Panasonic Viera TX40DSW504 

       Windows 11 Version 24H2 for x64-based System;

        Update for .NET Framework 3.5 and 4.8.1 for Windows 11, version  24H2 for x64; NET 8.0.18 Update for x64 Client

This worked well until a few weeks ago. Now it flashes for a while and then stops working or doesn't work at all.

If I connect my mobile via HDMI adaptor and the same cable to the TV it works perfectly

I have:as recommended

   Fully Power Cycled Everything

   Reinstalled the Display adapters and Universal Serial Bus controllers

   Carried out a BIOS/UEFI Reset

   Ensured that all BIOS & Chipset Drivers are up to date

I then installed HP PC Docs and Displays Diagnostics Windows 4.0.0.0

All diagnostics tests came back with OK except the current resolution of the TV is shown as 0x0

Model: Panasonic-TV; Caption: Generic Monitor (Panasonic-TV);Description: Generic PnP Monitor; Status: OK; Serial Number: 16843009; Manufacturer: MEI; Device: UID198147; PNP Class: Monitor; Port Type: Hdmi; Current Resolution: 0 x 0

Help would be appreciated!

[Max3Aj]

@Tamrac99, Hello and welcome to the HP Support Community!

Thanks for posting your question. I'm here to help you get things back on track.

I understand you're experiencing issues with your HDMI connection from your HP Pavilion 15-cs0013na to your Panasonic Viera TX40DSW504 TV after upgrading to Windows 11 24H2. You've already done a great job with initial troubleshooting steps. Let's go a bit deeper to isolate and resolve the issue.

Check Display Output Settings

Sometimes Windows defaults to "PC screen only" after updates.

• Press Windows + P and select Duplicate or Second screen only.
• Right-click on the desktop → Display settings → Scroll to detect displays manually.
• If the TV is detected, try setting it as an extended or duplicated display.

Force HDMI Detection

• Go to Device Manager → Expand Monitors and Display Adapters.
• Right-click and Uninstall the Generic PnP Monitor (Panasonic-TV).
• Click Action > Scan for hardware changes to re-detect the display.

Update Graphics Drivers (Manually)

Even if Windows says drivers are up to date, manually installing the latest Intel/NVIDIA drivers can help.

• Identify your GPU: Go to Device Manager > Display Adapters.
• Download the latest drivers from:
  • Intel Graphics Drivers
  • NVIDIA Drivers (if applicable)
• Install and restart.

Try Lowering the Refresh Rate

Some TVs don’t support high refresh rates from PCs.

• Go to Display Settings > Advanced Display Settings.
• Select the TV and set the refresh rate to 30Hz or 60Hz.

Check HDMI Port Functionality

• Try a different HDMI port on the TV (if available).
• Try a different HDMI cable (even though the current one works with your phone, PCs can be more sensitive to cable quality).

BIOS and Chipset Drivers

Ensure you’ve installed the latest BIOS and chipset drivers from HP:

• HP Pavilion 15-cs0013na Drivers Page

Look for:

• BIOS Update
• Intel Chipset Installation Utility
• Intel MEI (Management Engine Interface)

Try Safe Mode or Clean Boot

To rule out third-party software interference:

• Boot into Safe Mode with Networking and test HDMI.
• Or perform a Clean Boot: How to Perform a Clean Boot in Windows

Additional Diagnostic Tip

Since HP PC Hardware Diagnostics shows 0x0 resolution, it suggests the system is not receiving EDID (Extended Display Identification Data) from the TV. This could be a driver-level or handshake issue.

If All Else Fails

• Try rolling back Windows to a previous version (if the issue started after 24H2 update).
• Or consider using a USB-C to HDMI adapter if your laptop supports USB-C DisplayPort Alt Mode.

I hope the information shared has been useful and resolves your concern.

Wishing you a smooth and hassle-free experience ahead!

If this solution helped, please click “Accepted Solution” so others can benefit too. Don’t forget to hit the “Yes” button if you found this helpful!

Warm regards,

Max3Aj

HP Support

[Tamrac99]

Hi Max,

I had already checked:

Check Display Output Settings

Try Lowering the Refresh Rate

Check HDMI Port Functionality

BIOS and Chipset Drivers

I have now done this:

Try Safe Mode or Clean Boot

Force HDMI Detection

Update Graphics Drivers (Manually)

I  can't restore Windows 10 as it's too late. All drivers are up-to-date

All unsuccessful. Currently the TV picture is jumping around (flashing).

My computer doesn't support the USB-C DisplayPort Alt Mode.

"This could be a driver-level or handshake issue." Maybe - but how do I deal with this?

Any other ideas?

[Max3Aj]

@Tamrac99, Thanks for the detailed follow-up. 
Since you've already covered most of the standard and advanced troubleshooting steps, and the issue persists with the TV flashing or showing no stable signal, we’re likely dealing with a deep-level HDMI handshake or EDID (Extended Display Identification Data) communication issue between your laptop and the TV.

Let’s now try advanced fixes that specifically target HDMI handshake and EDID problems.

Advanced Fixes for HDMI Handshake/EDID Issues

Override EDID via Custom Resolution Utility (CRU)

Sometimes Windows or the GPU driver fails to read the EDID correctly. You can override it using a tool called CRU (Custom Resolution Utility).

Steps:

1. Download CRU from here.
2. Run CRU.exe and select your Panasonic-TV from the dropdown.
3. If no resolutions are listed, click "Import" and try loading a known EDID file (or create a basic one).
4. Add a resolution like 1920x1080 @ 60Hz under “Detailed resolutions”.
5. Run restart64.exe (included in the CRU zip) to restart the graphics driver.
6. Reconnect the HDMI cable and check if the display stabilizes.

Be cautious with CRU. If the screen goes black, boot into Safe Mode and delete the override using reset-all.exe from the CRU package.

Disable Fast Startup in Windows

Fast Startup can interfere with hardware initialization.

• Go to Control Panel > Power Options > Choose what the power buttons do.
• Click Change settings that are currently unavailable.
• Uncheck Turn on fast startup.
• Save and reboot.

Try a Powered HDMI Splitter or EDID Emulator

If the handshake is unstable, a powered HDMI splitter or EDID emulator can stabilize the signal between the laptop and TV.

• These devices sit between your laptop and TV and ensure consistent EDID communication.
• Look for EDID emulators on Amazon or electronics stores (e.g., Dr HDMI, Portta HDMI EDID Feeder).

Check for Panasonic TV Firmware Updates

Sometimes the issue lies with the TV’s HDMI firmware.

• Visit Panasonic’s support site for your model: Panasonic TX-40DSW504 Support
• Look for firmware updates or HDMI-related patches.

Try Linux Live USB (Optional Diagnostic)

To rule out Windows entirely, boot from a Linux Live USB (like Ubuntu) and test HDMI output.

• If HDMI works fine in Linux, the issue is definitely with Windows 11’s driver stack or EDID handling.
• If it fails in Linux too, it may be a hardware-level issue with the HDMI port or controller.

I hope this helps!

If my response resolves your issue, please click “Accepted Solution” to help others find the answer. Also, don’t forget to click the “Yes” button to say thanks!

Take care and have a great day.

Max3Aj

HP Support

[Tamrac99]

Hi Max, thanks for this. I'm away for 3 weeks so I will look at you suggestions when I return.

[Max3Aj]

Thank you for your response @Tamrac99. 

Please get back to us at your convenient time. 

Regards, 
Max3Aj