I've got a mid-2010 iMac, 21", i3 processor with 4gb RAM installed which has only one partially-usable USB port, which will power a 3rd-party mouse, wireless dongle, or a keyboard sometimes, but not an apple mouse or larger devices. Nothing happens at all when I plug things into the other 3 ports, other than a hub.

Using a 3rd-party powered-usb hub, I am able to use the computer, and can even use 3 of the 4 ports as the host port. The 4th port remains completely broken. I can get in though and enable ssh, bluetooth, and wake-for-BT options if needed.


  • confirm the computer is safe to use and should not start a fire (?)
  • any creative ways to get usb out of the "firewire" or display ports (?)
  • Are there other ways to diagnose and test the usb ports on iMacs?

AHT (Apple Hardware Test) (now called Apple Diagnostics) would not work initially; holding down option+d for online diagnostics gave me "Error code -3403D" which I think means that on this iMac AHT is not supported, without a CD, and I had to boot AHT from an old OSX installation disk 2, although I can't provide a good reference for that. Hardware test says "no issues." :-)

My favorite ACMT at my favorite AASP had previously told me that this iMac had a recalled Graphics card and I was lucky it worked at all. The known fix for USB was to switch the system board, which made it probably not worth the cost.

So it's essentially it is working as a non-critical production machine or small server... but I want to make sure it is safe, and please anyone let me know any further tips about how to debug USB on OSX.

I still need to check if the system is issuing any dmesg when things are plugged into the non-working usb ports, it might provide other clues. I'll also call back the AASP now that I got the error code, to make sure -3403d is not related to usb.

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    I don't think anyone can answer the 'is it safe' question without actually examining the hardware. The first thing to test is whether there is anything stuck in any of your USB ports or if they are physically damaged in any way. If they are fine physically then I would imagine there to be little risk of fire. If the only impairment is the lack of powered USB ports then your hub should do the job fine. – amergin Apr 2 '16 at 22:28
  • @amergin There is for sure no small objects stuck from the outside in any of the ports, and they are not lose or strange in any way physically. – forgotstackxpassword Apr 2 '16 at 23:36
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    I've now updated the post to reflect tests I did with a powered usb hub (works), as well as results of AHT (no errors). Cc: @amergin – forgotstackxpassword Apr 4 '16 at 20:37

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