Thursday, June 06, 2013

Mac USB port not working? Try an SMC reset.

I unplugged my 27" i5 iMac during a thunderstorm the other day. When I plugged it back in, my USB hub no longer charged our iPhones. It was dead.

This annoyed me, but the iMac is a few years old and that port has been well used. Perhaps I was just unlucky. Gradually though, I remembered that unplugging an intel iMac resets  the System Management Controller (SMC). That's normally done as a fix for problems, but perhaps it can also cause them.

So I repeated the reset and my USB port works again. For the moment anyway, I wouldn't be surprised if it fails later.

USB ports aren't listed as SMC controlled in Apple's knowledge base article, but SMC reset (and, with less evidence, NVRAM reset) is a common folk therapy for bad ports. This article listed other things that may (or may not) benefit from an SMC reset:

  • Erratic sleep mode performance, including not waking from or not entering sleep.
  • Mac portables (MacBook, MacBook Pro, MacBook Air) not responding to lid opening or closing.
  • Failure to respond to the power button being pressed.
  • MagSafe power indicator not displaying or displaying incorrectly.
  • Sluggish performance, even though Activity Monitor shows little CPU usage.
  • Target Display Mode not working correctly.
  • Battery not charging or taking excessive time to charge.
  • USB ports not working.
  • Bluetooth not working.
  • Fans running fast.
  • Display backlight not responding to ambient light level changes.

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