If a Pi fails to boot for some reason, or has to shut down, in many cases an LED will be flashed a specific number of times to indicate what happened. The LED will blink for a number of long flashes (0 or more), then short flashes, to indicate the exact status. In most cases, the pattern will repeat after a 2 second gap.
| Long flashes | Short flashes | Status |
|---|---|---|
| 0 | 3 | Generic failure to boot |
| 0 | 4 | start*.elf not found |
| 0 | 7 | Kernel image not found |
| 0 | 8 | SDRAM failure |
| 0 | 9 | Insufficient SDRAM |
| 0 | 10 | In HALT state |
| 2 | 1 | Partition not FAT |
| 2 | 2 | Failed to read from partition |
| 2 | 3 | Extended partition not FAT |
| 4 | 4 | Unsupported board type |
| 4 | 5 | Fatal firmware error |
| 4 | 6 | Power failure type A |
| 4 | 7 | Power failure type B |