Mac USB Problems

I’ve been having USB issues with my MacPro3,1. I’ve had the Mac Pro for about four years, but it’s otherwise been running like a champ.

A while back, I started having issues with a USB hub that was plugged into the back of the Mac. I replaced the cable, and things seemed to be fine. Until a while later, when the cable seemed to fail – then I replaced the hub, and all seemed fine.

Then the new hub was starting to have issues. So, I replaced that hub with another hub and new cable and things have been working swimmingly for a few months.

Then, this morning, all the USB ports on the back of the Mac seemed to go wonky – including one port which can recognize a device but always not power it properly. The front ports on the Mac, however, seem fine – sometimes.

I’ve zapped PRAM, I’ve booted into Safe Mode, and I’ve run USB Prober (from the Developer’s Tools) but… the prober tool doesn’t always recognize the device, either – but leads me to believe that every port is running as it should be running.

How could I, without introducing any new USB devices to the chain, be over-runing the system – especially when I’ve removed all USB devices and am still having issues with individual ones (like the wired Mac keyboard, but only sometimes in some ports but not at all in others)?

  • I can plug something like a USB flash drive into a port on the back and it might seem fine – it illuminates, but doesn’t always show a mounted drive (but always does on reboot, irrespective of port).
  • I can also plug Apple’s wired keyboard into a front port and it sometimes works, and sometimes doesn’t. It doesn’t seem to work at all in any of the rear USB ports.
  • I can see a Logitech webcam via USB Prober in one port, and its face illuminates when I open Photo Booth – then its face goes dark and Photo Booth doesn’t show an image.
  • If I plug that same Logitech USB webcam into just about any other USB port, the system doesn’t recognize it at all.
  • I tried reinstalling KEXT files, and that just forced me to reinstall Snow Leopard (which was painless, for whatever it’s worth). No go.
  • Someone in the comments suggested plugging my iPhone into ports to see if power was passing through them – and it was for all but the inner most rear USB port. Ouch.

I can’t imagine that it’s a failing power supply, but can’t help but wonder if I’m missing a software step after going through all of that. I’d hesitate to reinstall the OS only to find out the hardware was still the root cause. Who knows? Maybe Lion will fix the problem (and, at this point, I’m willing to wait a few more weeks for that install before either taking ‘er in or finding a Seattle-area Mac professional to help troubleshoot this on-site).

I believe it’s a hardware issue, but short of replacing the motherboard… ouch. “Repairs and Service Coverage: Expired.” Worse yet? Blake (from our community) sent me this link suggesting that this problem is known throughout my Mac Pro revision / line.

47 thoughts on “Mac USB Problems”

  1. I don’t think its a MoBo issue this might sound stupid but when it came to my desktop I was having a similar issue. I just changed my CPU case (so essentially I went for new USB ports and a less-dusty computer inside) and it works like a charm now.Of course, USBs fail if you connect too many at the same time because your Power Unit can’t handle it, but that isn’t your problem as you stated above.

  2. Question: Can you charge anything off the ports? You can get cables that just provide power to a device via USB. I think this will help you determine if its a driver/power issue. USB ports are always hot (power going to them). So if you plug your “power only” USB cable in and get power all the time, it may be a KEXT issue. Also, get a USB cable, strip it and test the black and red wires and see what volts/amps they are at.

    1. Interesting. I can charge my iPhone from two ports on the back. The third one does not push power to the iPhone, but can sometimes power a Flash drive.

      How might I go about checking / replacing the appropriate KEXTs – copying them from another installation, assumedly. Which ones?

      1. Silly question before I go further: Are the ports loose? Maybe a flash drive or another device was in the port and someone or something bumped it? I am wondering if there is a short and/or the USB port is not seated correctly on the mobo. Does jiggling the cables in the ports help?

          1. Personally, I would do a wipe of the system and just start fresh again. I dont know really how to replace or repair the KEXT any other way. In the hackintosh world, you would use KEXT Helper, but this is not a hackintosh.

      2. Silly question before I go further: Are the ports loose? Maybe a flash drive or another device was in the port and someone or something bumped it? I am wondering if there is a short and/or the USB port is not seated correctly on the mobo. Does jiggling the cables in the ports help?

      3. Something you may consider trying is an SMC reset on your system since it seems to be a power regulation issue with the ports

  3. Strangely and irrelevantly, I’m having problems with a USB hub. It’s one of the 24-port “monster” hubs you see out there on ThinkGeek and Newegg. Devices occasionally just disconnect. I suspect ESD.  Today I unplugged it to reset the device connections, and it rebooted the computer.   No BSOD, just rebooted. Wait, what?

  4. I didn’t see you mention it, but did these devices work on another machine AFTER the issue? I say “after” just in case it’s killing your peripherals.

      1. No surprise there. I’ve seen some weird USB problems that I could only attribute to ESD or erroneous power levels.  ESD damage can be cumulative, you know.

          1. Not that I know of, unless you have experience in repairing printed circuit boards.  If you’re lucky, it’ll be a solder point. If you’re *really* lucky, it may have been right after an upgrade of some kind which you can undo. Did you do anything unusual to it before it started?

          2. Ack. No idea. I haven’t been inside in ages. Well, apart from an hour ago when I eliminated a few dust bunnies (which weren’t so plentiful, really).

          3. That didn’t happen to make it worse, did it?  If so, look for anything loose, rattling, etc. Also, major culprit, condensation. I saw that bottle of compressed air.

      2. No surprise there. I’ve seen some weird USB problems that I could only attribute to ESD or erroneous power levels.  ESD damage can be cumulative, you know.

      3. No surprise there. I’ve seen some weird USB problems that I could only attribute to ESD or erroneous power levels.  ESD damage can be cumulative, you know.

  5. HI Chris,
    Silly idea, but something that helped me with constant disconnect on certain USB devices: run Onyx and clear every available cache. After that, I had no further problems…

  6. Chris in case you haven’t seen my replies, you put a Kernel extension in that is not letting your install boot, you’re gonna need to do a reinstall.  Once that’s back up do an SMC reset to try and resolve the USB issue

    1. Nah. They will repair any computer for a flat rate fee if its out of warranty. Either spend an extra 250 for applecare (or whatever it runs for these days) or spend about $310 per repair. Not a horrible deal.

  7. Windows hardly ever give problems like this, and you could buy a new computer for the cost of repairing a mac

  8. Exact same thing here. Just got my MacBook Pro back today from the shop. Spent $310 and they replaced the logicboard, the entire screen assembly, and a new harddrive. Oh they also overnighted the it to and from their repair facility. Whoo! not a bad price for all of that!

  9. OOps. Don’t get that particular USB card, it is one USB controller with a built in hub (so they all vie for the same single port. I’ll do some more research, but I do recommend adding more USB ports to your Mac.

    1. Okay, so I got the USB card today.
      The “Best Connectivity 4 Port USB 2.0 PCI-Express X1 Card SD-PEX20052”
      Bought from Amazon, $20, plugged in, and removed my hub from the equation.
      All the problems I had where my TV controller would need a reset when I plugged in/unplugged my iPhone went away. All other momentary glitches related to USB went away.
      No drivers to install, nothing. Just plug in, turn on, recognized in System Profiler, both under PCI cards and under USB ports. No hubs in use, no need to connect the card to power.
      I have the same Mac Pro as you. Easy as pie, worked immediately, USB humming along beautifully now.
      I Highly recommend doing this and ditching your hub. I predict even the problems with your built in USB will go away.

  10. Maybe it’s an oxidation/contamination problem, so try cleaning the contacts with some alcohol.

  11. Chris, I’ve admired yoUr work since you were on “Screen Savers” with my friend Leo Laporte. I’m actually tickled that I might have a clue to your problem, but unfortunately not a cheap fix. I am Apple Certified hardware technician and have seen this problem on many 2008 Mac Pro machines. You are a high profile guy, you might want to try “back channeling” through the Apple marketing division.

    Replacing the MOBO AND THE TWO (front and back USB controllers) will be expensive and the problem will reappear, eventually. You also may have a problematic USB device exacerbating the failure. Check all devices on another machine if you can.

    If you are really attached to your Mac Pro, I’d recommend going with the far less expensive route by adding the four or five port ePCE card. (note: the five port has one inside as well as the four outside).

  12. You can still Daisy Chain USB hubs through the new card. POwered USB hubs work best as these send a signal back to the SMU to use the power elsewhere. The real root of the Problem is in the design of the 2008 MOBO. 2009 models improved on the issue, but not completely cleared until 2010 models using independent controllers for each pair of USB ports.

  13. Chris, can you update what your eventual solution was? I just lost my two front and two of three rear USB ports AND my bluetooth (but not WIFI) on my 2008 MacPro. The event was: whilst scanning an 11 page document with a ScanSnap S1300i I connected my Garmin forerunner 210 to charge and upload activity. So, looks like 2 front and 2 rear USB ports must be separate from the third rear port, somehow. Why the bluetooth, on a separate bluetooth/wifi card, dropped out simultaneously, is beyond, esp considering that the wifi continues to function.

Comments are closed.