Dead USB port(s)

[ChrisDx]

Hi;

I have an iMac 27" with 4 USB ports. I was having issues with mounting and ejecting external drives and it turns out that the port (at the back of the iMac) to which i had connected a powered USB hub was dead.

To make a long story short, I reset the SMC and now, while that port is working, a different one is dead. I'm running MacOS 10.11.3.

Any ideas?

Chris

 

[Fishrrman]

I'd try resetting the SMC once or twice more.

Also, use the System Information utility to check all the USB ports.
Might try plugging something into the dead port, to see if System Information "picks up" on it or not ...

 

[ChrisDx]

Hi Fishrrman;
I've reset the SMC three times and a different port is dead after each time. I check each port by simply connecting my keyboard/mouse into each.
The System Information does not show any device in the "dead" port.
Chris

 

[Fishrrman]

It's odd that each time you do a reset, a DIFFERENT port "goes dead" on you.

If it was an actual hardware failure, I would think THE SAME port would remain dead all the time.

Seems like something in the software (port driver kext?) isn't working as it should.

Is this computer still under AppleCare, by any chance?

Another thought:
Try booting from a "freshly-installed" OS on ANOTHER drive, if you have one available.

Another thought:
Unplug the iMac from the wall and remove the RAM DIMMs.
Let it sit for an hour or so.
Then re-install the RAM and reboot. Any change?

 

[ChrisDx]

It's odd that each time you do a reset, a DIFFERENT port "goes dead" on you.

If it was an actual hardware failure, I would think THE SAME port would remain dead all the time.

Seems like something in the software (port driver kext?) isn't working as it should.

Is this computer still under AppleCare, by any chance?

Another thought:
Try booting from a "freshly-installed" OS on ANOTHER drive, if you have one available.

Another thought:
Unplug the iMac from the wall and remove the RAM DIMMs.
Let it sit for an hour or so.
Then re-install the RAM and reboot. Any change?

Apparently, the SMC reset is heat sensitive. I left the Mac unplugged for a couple of hours before trying it again. Hallelujah, it worked!