A Raspberry Pi isn’t just a credit-card-sized gateway to exploring the vast world of computing and electronics. The single-board computer is also capable of communicating its current operating state and whether there are any boot issues to the user.
Want to know how your Raspberry Pi is feeling? In most cases, just taking a look at the LEDs on the board should be enough. We will take a close look at these status LEDs and explain how you can determine what they indicate.
What Are the Different Status LEDs On the Raspberry Pi?
The number and arrangement of LEDs differ across Raspberry Pi models. There are four LEDs in total on most Raspberry Pi boards: two next to the power port (they may be closer to the GPiO header on some models) and two on the Ethernet port. The Raspberry Pi Zero has one LED next to the power port and the very first Raspberry Pi, the Model B (now discontinued), had five LEDs on the board.
On a Raspberry Pi 4B, you will find two status LEDs, a red and a green, along the edge leading off from the power port to the MIPI DSI port. The red LED is labeled PWR while the green is labeled ACT.
There are also two LEDs on the Ethernet port, green (LNK) and yellow (100/10M), which communicate information about the Ethernet connection. The green LED indicates activity over the Ethernet network and flashes during data transfers, while the yellow LED indicates a 100 Mbit Ethernet link on older models or a 1000 Mbit link on Raspberry Pi 3B+ and 4. The yellow LED remains off for lower-speed connections.
These LEDs remain active during typical operation, but it is possible to turn them off to save power in your low-power or portable Raspberry Pi projects.
Below, we are going to be taking a closer look at the status LEDs directly on the board. The information they communicate is of much primary importance, compared to the Ethernet LEDs.
What Does the Red Status LED Indicate?
The red status LED (PWR) is as its name suggests responsible for indicating whether the Raspberry Pi receives sufficient power to be turned on. On older models, it would turn on immediately after a power supply was connected to the Pi. But in later models, starting from the B+, the red LED is also capable of indicating if a power supply is not providing enough voltage required by the Raspberry Pi. In this case, it would either flash or turn off.
If the power LED is not functioning as expected, it is a good sign that you should connect a better power supply to the Raspberry Pi. You can also learn more about how to reduce power consumption in your Raspberry Pi projects.
What Does the Green Status LED Indicate?
The green status LED is designated as ACT (short for "activity"), and it is a bit trickier to decipher than the power LED. This LED is the only one present on the Raspberry Pi Zero models. Generally, it indicates SD card activity.
This LED remains solid and consistently on during regular operation. It flashes when applications are running—that is, when read and write operations are ongoing—and should flash frequently in an irregular pattern when the Raspberry Pi is booting. However, it may not turn on if there are any issues with your installation or the SD card itself.
The ACT LED also flashes in specific patterns to indicate problems with booting. This works differently on models earlier than the Raspberry Pi 4B due to changes in how the bootloader works on the 4B.
Raspberry Pi 3B+, Pi Zero and Earlier Models
The table below describes what different green LED flashes mean on a Raspberry Pi 3B+, Zero, and earlier models (bar the original Pi Model B).
Flashes | Meaning |
|---|---|
3 flashes | start.elf not found |
4 flashes | start.elf found but not launchable (corrupt) |
7 flashes | kernel.img not found |
8 flashes | SDRAM not recognized. You need newer bootcode.bin/start.elf firmware, or your SDRAM is damaged. |
Constant, irregular flashes | Read/write operation |
Raspberry Pi 4, Pi 400 and Compute Module 4
The Raspberry Pi 4, 400, and the Compute Module 4 all boot from an EEPROM on the board, unlike older models which use the bootcode.bin file in the boot filesystem on the SD card.
In these models, the LED patterns are a bit more complex which means that they can relay more information about the boot sequence. The ACT LED will blink for a certain number of long flashes (0 or more), followed by a sequence of short flashes, to indicate the exact status. Usually, the pattern will repeat itself after a two-second gap.
Long Flash | Short Flash | Meaning |
|---|---|---|
0 | 3 | Generic failure to boot |
0 | 4 | start.elf not found |
0 | 7 | kernel.img not found |
0 | 8 | SDRAM Failure |
0 | 9 | Insufficient SDRAM |
0 | 10 | In HALT State |
2 | 1 | Partition of boot device not FAT |
2 | 2 | Failed to read from boot partition |
2 | 3 | Extended Partition not FAT |
2 | 4 | File signature/hash mismatch - Pi 4 |
3 | 1 | SPI EEPROM error |
3 | 2 | SPI EEPROM is write protected |
3 | 3 | I2C error |
3 | 4 | Secure-boot configuration is not valid |
4 | 4 | Unsupported board type |
4 | 5 | Fatal firmware error |
4 | 6 | Power failure Type A |
4 | 7 | Power failure Type B |
Any one of the statuses above indicates a boot problem and may require that you either change the microSD card or upgrade/update the bootloader. Newer versions of the Raspberry Pi 4 bootloader (starting from version 2020-04-16) will display a diagnostic message at boot time on a connected HDMI display.
Raspberry Pi 1 Model B
The original Raspberry Pi Model B from 2012 used firmware that depended on the loader.bin file and therefore the flashes on the LED meant slightly different things.
Flashes | Meaning |
|---|---|
3 flashes | loader.bin not found |
4 flashes | loader.bin not launched |
5 flashes | start.elf not found |
6 flashes | start.elf not launched |
7 flashes | kernel.img not found |
It Is Easy to Troubleshoot Boot Issues on a Raspberry Pi
The status LEDs on the Raspberry Pi are pretty insignificant during normal operation, but they quickly become important when you need to diagnose boot issues. While there are many reasons why a Raspberry Pi won’t boot up, checking the status LEDs and counting the flashes on the green ACT LED is a great way to begin finding out why.
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