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I recently got my first Raspberry Pi (model 3 B+) plus a starter kit from Adafruit, and I have encountered my first challenge: boot the darn thing. The starter kit came with a micro SD with NOOBs installed, and without a way to check I will assume that it is current.

Problem: The power LED is blinking (solid 2sec, four 1Hz blinks, four 2Hz blinks, repeat), and the HDMI monitor shows the rainbow screen and a yellow lightning bolt in the upper right. I've looked into the "blinking power LED" issue and concluded that this is bad (yes, I've tried a different USB cable with the same effect). The ACT LED does nothing.

But beyond that, is there a specific meaning to the blinking power LED? That is, is the blinking pattern that I noticed significant or does it simply indicate "bad"?

John Cox
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I thing it could be 2 problems described here: Raspberry Pi with boots up with Rainbow screen and here: What does the lightning bolt mean?

The second one also could explain blinking power LED. Remember that Rapsberry Pi require quite high current power supply about 2A or so on. In typical power supply, when your device try to drain to much current, the voltage is dropping.

In first place I will try to solve the problem with power. After that deal with boot problem.

Łukasz Jakubek
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The Boot Problems Sticky mentions the problem you described.

If you have one of the latest PI 3B+ which won't boot and it keeps stuck on the rainbow screen, while also displaying the under voltage (lightening bolt) icon, and/or the red LED flashing then you are simply are using boot code that is too old. Please download the very latest version of Raspbian, or do an upgrade to it.

Apparently this is because the intended diagnostic is being sent to the wrong pin.

This is not an intended diagnostic but a side effect caused because the Pi3B+ voltage detector is part of the regulator chip with no external pin. It needs to be read from a register which requires matching firmware.

Milliways
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If the red PWR LED is flashing, it indicates that voltage from your power supply drops below 4.63V. Seems there is a problem with your power supply or an overload by attached peripherals, e.g. USB-devices without its own power supply. Look at What do system LEDs signify? for further information.

As @Milliways wrote in his comment this may not work if you use the wrong firmware. To ensure your firmware is up to date you should test your RPi 3B+ with the latest official Raspbian Stretch Lite.

Ingo
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Not sure if the question has been answered yet but...

Short Answer: Try reformatting the SD Card with a different OS or which SDs

Long Anser: The code (4 short blinks, 4 long blinks) for me meant that the OS (which was OpenElec) would not boot. I tried reformatting the card...no luck. Flashed the SD card with OSMC and VOILA it worked. I think that the code means that the OS boot files are corrupted, won't know for sure without more testing.

Squidy P
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