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Troubleshooting / Pi 4 Boot

Raspberry Pi 4 Will Not Boot

Fix Raspberry Pi 4 boot issues. Check the correct HDMI port connection, verify SD card health, and diagnose problems with LED indicators.

Raspberry Pi 4Boot IssuesBy Vilros

Overview

Is your Raspberry Pi 4 not booting or showing only a rainbow screen? The two most common causes are using the wrong HDMI port or a faulty SD card.

This guide will help you diagnose and fix Raspberry Pi 4 boot problems.

Check the HDMI port (most common issue)

Important: When using a single HDMI connection on Raspberry Pi 4, the cable MUST be connected to HDMI0 (the port closest to the USB-C power port).

Fix wrong port issue:

  1. Identify HDMI0: This is the micro HDMI port closest to the USB-C power connector
  2. Disconnect your HDMI cable
  3. Connect to HDMI0: Plug into the port nearest the power connector
  4. Power on your Pi

Rainbow screen symptom:

If you see only a rainbow square or colored screen on your display, your HDMI cable is plugged into HDMI1 (the wrong port) instead of HDMI0. Simply move it to HDMI0.

Note: This is specific to Raspberry Pi 4 and Pi 400. Pi 3 and earlier models have only one HDMI port and don't have this issue.

Check the SD card

A corrupt or improperly flashed SD card will prevent booting:

  • Reflash your SD card: Write a fresh Raspberry Pi OS using Raspberry Pi Imager
  • Use quality SD cards: Class 10 or better from reputable brands (SanDisk, Samsung, Kingston)
  • Check the card is seated: Remove and reinsert the microSD card, making sure it clicks in firmly

Follow the official instructions: raspberrypi.org/documentation/installation/installing-images

We recommend using Raspberry Pi Imager software for best results.

Check LED indicators

The LED lights tell you if the Pi is reading the SD card:

  1. Power on the Pi 4 with the SD card inserted
  2. Observe the LED lights on the board

Normal LED behavior:

  • Red LED: Should turn on solid (indicates power)
  • Green LED: Should flash periodically (indicates SD card activity)

Abnormal LED behavior indicates SD card problem:

  • Green LED never flashes: Pi cannot read the SD card
  • Green LED flashes rapidly without stopping: SD card read error
  • No red LED: Power supply problem

If you do not see the green light turn on at all, or if the green light flashes repeatedly and does not stay on for more than a second, the SD card is faulty and needs to be reflashed.

Further help

If you've checked the HDMI port and SD card and confirmed everything is correct: