As it turns out, this problem is almost always rooted in the config.txt file that your Raspberry Pi installation maintains. If it’s not a temporary glitch produced by the cached folder, it’s probably a setting that the OS maintains in the config file. With older displays, this issue might also occur due to a resolution mismatch, due to insufficient power, or due to insufficient HDMI signal that needs to be boosted manually. Before you enforce any of the other potential fixes featured in this article, start with the following quick fixes:
Check that the HDMI cable is correctly connected at both ends. Just disconnect the cable, blow air into the port, then reattach it.Check that the SD card is properly attached. Even if the lights turn on, there may still be problems, which you must physically inspect.If you’re using an HDMI adaptor, try whether it works with other devices. Often, the problem is with the adaptor, and changing it appears to be the only possible option.
If none of these quick fixes worked, move down below and start troubleshooting with our collection of user-confirmed fixed.
1. Remove SD Card and Reboot
If you started getting this error after connecting your Raspberry Pi to a TV that was already on, the fix might be as simple as removing the SD card and rebooting the monitor that failed to acquire the signal. Note: This fix is often effective due to the fact that the HDMI signal outputted by the Raspberry Pi is weak by default and a lot of older TVs might not have the ability to dynamically adjust the frequency to be able to pick up the signal. However, if you reconnect the SD card after the HDMI source is connected, the TV will have ample time to adjust the frequency to display the video output. If you already tried this and there’s still no signal coming out from your HDMI source, the next step should be to check the config.txt file for any inconsistencies (follow the next method below).
2. Edit the config.txt file (if applicable)
If you experience this issue while connecting your Raspberry Pi to a TV monitor via HDMI and you installed the selected OS on an SD card, the problem is almost certainly appearing because the boot sector of the SD is normally accessible directly from Windows and not from an HDMI hotplug. If this scenario is applicable, you can fix the issue by editing the config.txt file and adding a line that will force the signal to go through HDMI. Note: This method is only applicable in scenarios where the RPI device is outputting no signal to older LCD TVs via HDMI. In case this scenario is applicable, follow the instructions below to force the HDMI display on your device:
3. Boost the HDMI Signal (if applicable)
As we discussed above, most Pi models will output weak HDMI signals. This is certainly not a problem with newer TV models that were released after 2012 when the industry standard changed, but older devices might not notice the Pi’s HDMI signal and the frequency negotiation might not happen. In this case, you’ll need to do a series of adjustments inside the config.txt file to ensure that the Pi device believes the monitor or TV is really there and boost the HDMI signal in order to ensure that the data exchange is started. Note: If you’re using an unusually long HDMI cable, switching to a shorter, better-quality cable will certainly help. Also, it’s important to ensure that your Pi’s power delivers 1A and not 500mA. Here’s a quick guide on the modifications that you need to enforce in order to boost the signal for HDMI connections:
4. Re-write Rasberry Pi Image
If you’ve come this far without a viable fix, it’s about time to investigate whether you’ve correctly written the Raspberry Pi Image to the card that you’re using when attempting to output to HDMI. To carry on this verification, insert the card into a MAC or PC via a card reader and explore the root directory for the following files:
bootcode.binfixup.datstart.elfconfig.txt
If any of these files are missing, this video output issue is clearly caused for an image issue. In this case, the only solution available is to simply re-write the Raspberry Pi Image using Raspberry Pi Manager. Note: You can carry on this operation either on a PC or on a Mac. Here’s how to do this:
5. Use a smaller HDMI screen (if applicable)
If you are experiencing this issue while using a microcomputer like Pi Zero, keep in mind that none of the fixed features in this article will allow you to successfully connect it to a large HDMI screen with a big diagonal. Note: Micro computers like the Pi Zero are simply not powerful enough to support a connection that requires this much power. Although theoretically, Pi Zero is perfectly capable of doing 1920×1080 @ 60 Hz, it can only do so with displays that are very energy efficient and are not at all reliant on the outputted for power. If this scenario is applicable, all you can do is lower your expectations and plug in your Pi Zero to a smaller HDMI screen. There is no definitive guide o the maximum HDMI screen size since this will vary a lot from manufacturer to manufacturer.
6. Upgrade power supply or lower display resolution
If you’ve come this far without a resolution, there’s a big chance you’ll need to use a more powerful supply and might even need to adjust the display output to a higher resolution. It’s not uncommon to experience this NO Signal issue with your Raspberry Pi device because the current power supply has issues displaying the output at the current resolution. Update: This is a lot more common in scenarios where you have your device connected to a 4K display. If this scenario is applicable, you have two ways of fixing the issue:
7. Use Noobs Lite to re-flash Raspberry Pi
If you used the newer Rasberry Pi Image tool or the regular NOOBS to create the image and you see 4 flashes in the ACT LED and no video output, there’s a big chance the installation is corrupt. In case you already tried the method above with no success, one quick fix that was confirmed by a lot of users is using the Noobs Lite utility instead. Note: You can avoid the instructions below altogether and go for the easy route; buying a NOOBS SD card. These things are available with a lot of retailers and will typically go for less than $20. If you don’t want to spend the extra cash for a fix that might or might not work, follow the instructions below and use the NOOBS (New Out of Box Software) Lite tool to install and reinstall the OS before attempting to output to HDMI once again:
8. Use a different display to downgrade resolution (if applicable)
If you are experiencing this issue on a Raspberry Pi 4 while attempting to connect it to an older TV, there’s a big chance you are getting no signal (or a black screen) because the display does not support the resolution outputted by your PI. In this case, the easiest way to fix your problem is to connect your PI4 device to a more modern device with a high screen resolution long enough to downgrade the outputted resolution on your microcomputer. If you’re using Raspberry Pi OS, connect your Pi to a higher resolution display, then go to Preferences > System Configuration. Next, go to Screens > HDMI > Resolution and select a lower resolution. Once the resolution has been downgraded, re-connect your Pi to the older display and see if the HDMI output issue has been fixed.
9. Use the HDMI-0 port (only for Pi4)
If you’re using a Pi4 device, make sure you are using the HDMI-0 port – that’s the one closest to the USB-C power jack. Unless you use this HDMI port, you’re bound to run into issues with a higher-screen display that requires more power. After you’ve ensured that you are using the HDMI-0 port, ensure that you have the correct input selected on your GV or monitor before booting up your Pi once again.
