Not a duplicate of this RPi.SE question, as I'll explain in a moment. GPIO.RPI_REVISION returns 3.

As far as I can tell, looking at my B+, there are no LEDs labeled: OK, FDX, LNK or 10M. There are two embedded in the Ethernet port, and two on the opposite side of the board. The ones on the Ethernet are unlabeled, but I can guess what they mean. The other two are labeled ACT and PWR.

PWR only turns on once in a great while. My RPi is running just fine, and the PWR diode is unlit (which others say should never happen). This is the one that confises me the most.

AMP seems to turn on under I/O heavy load. (Seems to be the equivalent of the old OK LED).

What do these lights signify?

  • My B+ only seems to have two LEDs, ACT (activity) and PWR (power). ACT flashes with SD card activity (although other software modules can also drive the LED) and PWR is on while 5V power is available. If your PWR isn't on perhaps you have a poor power supply. Mine has no Ethernet LEDs.
    – joan
    Commented Nov 25, 2014 at 17:32
  • 1
    There are another two build into the Ethernet, if you look closely in the corners.
    – PythonNut
    Commented Nov 25, 2014 at 17:43
  • 2
    So there are. I guess the yellow/orange is 100M and green is activity.
    – joan
    Commented Nov 25, 2014 at 17:57
  • Can you find your board on any official site that looks like that? Maybe its a counterfeit?
    – Piotr Kula
    Commented Nov 25, 2014 at 20:00

1 Answer 1


I believe the following is correct for the B+.


  • on if power OK
  • flashes (or goes out) if the power drops below about 4.63V


  • steady on if no SD card during boot

  • irregular flashes for SD card access

Ethernet Socket Left LED (yellow)

  • on 100-Mbps connection

  • off 10-Mbps connection

Ethernet Socket Right LED (green)

  • on if link established

  • flashes for port activity

  • off if no link is established




  • 1
    Ah, thank you. I suspect my power cable has a larger than normal voltage drop.
    – PythonNut
    Commented Nov 27, 2014 at 21:23
  • I usually power my Pis via the expansion header or back-powered through the USB ports (back-powering via the USB ports is not an option for the B+).
    – joan
    Commented Nov 27, 2014 at 21:28
  • What does ACT stand for? Commented Aug 20, 2016 at 16:48
  • 1
    @CiroSantilli巴拿馬文件六四事件法轮功 ACT stands for activity. It can be configured to show different types of activity but the default is to show SD card access.
    – joan
    Commented Aug 20, 2016 at 16:57

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