Raspberry Pi Act LED Error Patterns

If your Raspberry Pi board isn't booting, and the green 'Act' LED is flashing, count the number of flashes to look up which of the following issues that indicates. This is an excerpt from the full forum post at https://www.raspberrypi.org/forums/viewtopic.php?t=58151;

Error ACT LED patterns
While booting, the ACT LED should blink in an irregular pattern, indicating that it is reading from the card. If it starts blinking in a regular, Morse code-like pattern, then it is signalling an error. 

If it blinks just once, it could be that you have a Raspberry Pi with SDRAM from Micron. If the processor has a logo showing an M with an orbit around it, then using the latest software should solve your problem. Also make sure you are using a 4GB SD card, as a 2GB won't work in this particular case.

These are the other patterns that the ACT LED might show during a failed boot, together with their meanings:

  • 3 flashes: start.elf not found
  • 4 flashes: start.elf not launch-able (corrupt) See below:
  • 7 flashes: kernel.img not found
  • 8 flashes: SDRAM not recognized. You need newer bootcode.bin/start.elf firmware, or your SDRAM is damaged

If you have an older model of the Pi, you should note that firmware before 20th October 2012 required loader.bin, and the meaning of the flashes was slightly different:

  • 3 flashes: loader.bin not found
  • 4 flashes: loader.bin not launch-able (corrupt) See below:
  • 5 flashes: start.elf not found
  • 6 flashes: start.elf not launch-able
  • 7 flashes: kernel.img not found

potential reason for 4 flashes.
Note that 4 flashes could be an indication of a more or less broken SD-card connector. If Databit 1 is connected, but one of the other three Databits doesn't make contact, so the SD-card only works in 1-bit (SPI) mode, then this will lead to the four flashes error! Check if all pins of your card holder make good contact with the card!

Try the most basic set-up
If you are having a hard time getting the Pi to boot, try stripping it down to its most basic set-up. Disconnect any extraneous USB devices, and try booting with only the video and the power cable connected. If you have to press keys to switch video mode, you will need to connect some kind of keyboard, but try it with the most basic, no frills USB-keyboard. This can help ease the boot process in some circumstances. 

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