Raspberry Pi 4 — HDMI Not Working (No Signal / Black Screen)

This guide helps you quickly troubleshoot Raspberry Pi 4 HDMI output issues (no signal, black screen, wrong resolution, etc.). Most problems come from cable/port selection, monitor detection, power, or display mode configuration.

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✅ Quick Checklist (Most Common Fixes)

1) Confirm you’re using the correct HDMI port

Raspberry Pi 4 has two micro-HDMI ports:

• HDMI0 (primary) = closest to the USB-C power port
• Try HDMI0 first

2) Check cable & adapter

• Use a proper micro-HDMI → HDMI cable (Type D → Type A)
• Avoid cheap adapters + old HDMI cables (can cause “no signal”)
• Try a different cable if possible

3) Check monitor input & hotplug

• Set the monitor to the correct HDMI input (HDMI1/HDMI2)
• Plug HDMI in before powering the Pi (some monitors don’t detect hotplug reliably)

4) Power supply matters (very common cause)

Pi 4 needs a solid 5V 3A USB-C power supply.

• Weak power can cause partial boot + no HDMI output
• Official Raspberry Pi PSU recommended

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1) Is the Pi Actually Booting?

Look at LEDs:

• Red PWR LED: should be solid
• Green ACT LED: should blink during boot/activity

If you can access the Pi over the network:

• Try ping/SSH (if SSH was enabled and you know the IP)
  • If it boots but no display → likely HDMI config/cable/monitor
  • If it doesn’t boot → SD card / OS / power issue (HDMI may be fine)

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2) Force HDMI Output (config.txt Fix)

If the Pi boots but the screen stays black or shows “No Signal”, force compatible HDMI settings.

Where to edit config.txt

Depends on your OS version:

• Raspberry Pi OS Bookworm: /boot/firmware/config.txt
• Raspberry Pi OS Bullseye / older: /boot/config.txt

💡 You can edit this by inserting the SD card into a PC and opening the boot partition.

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Option A: Force Safe HDMI Mode (fastest)

Add this near the bottom of config.txt:

hdmi_safe=1

Option B: Force HDMI Detection + 1080p (for “No Signal” monitors)

Use this if the display doesn’t detect the Pi:

hdmi_force_hotplug=1

hdmi_group=2

hdmi_mode=82

hdmi_mode=82 = 1080p @ 60Hz

Option C: If 4K was forced and your monitor can’t handle it

Remove any 4K forcing lines (if present) and use Option B to force 1080p.

3. Rainbow Square → Then Black Screen

If you see a rainbow splash briefly, the Pi likely starts output but switches to a mode your monitor rejects.

Try Option B (1080p) above.

You can also try swapping KMS overlays (advanced; only if needed):

Find this line (if present):

dtoverlay=vc4-kms-v3d

Try replacing with:

dtoverlay=vc4-fkms-v3d

Then reboot and test.