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September 23, 2020

USB Failed Enumeration Shows Unknown Device

Hmmm.  I just read an interesting post on TenForums, wherein a user describes plugging in “just one more” USB device. When he does that, instead of mounting the drive in Explorer, it shows up in Device Manager as an unknown device instead. The parenthetical error explanation reads “(Device Failed Enumeration).” Though I hadn’t seen this before, I’ve seen plenty of the more familiar “(Device Description Request Failed)” error explanation. That one can be a trial to fix, but the fix for the enumeration error — which TF poster @RickC asserts is a “longstanding Windows enumeration bug (since Vista) whereby if you plug/unplug multiple USB devices into different ports each time, eventually the registry hits an enumeration limit.” Next stop: the Unknown device entry you can see in the lead-in graphic for this story.

Easy Fix for USB Failed Enumeration Device

The NirSoft USB Device Viewer utility, aka USBDeview.exe, offers a way to clear out stale USB device entries so that the enumeration count is reduced and the error can be avoided. Once you fire this tool off with a right-click to “Run as Administrator…” you can sort its entries by clicking on the “Connected” column heading, as shown in the next screenshot. You can right-click individual entries that are greyed-out at left (there’s one showing in that image, at the very top), then select “Uninstall selected device(s)…” (depending on whether you select one or multiples, it changes from singular to plural).

Once you uninstall the absent items, the USB device count will go down (sometimes drastically). And usually, you can then plug the original offender back in and have it mount in Explorer (and show up in DevMgr) as just another USB device. Good stuff!

USBDeview showing not connected devices

Right-click on items with a grey symbol at left (top), then select “Uninstall selected device…” (or devices, if plural) from that menu.
This lowers the USB device count so enumeration shouldn’t fail.
[Click image for full-sized view]

All I can say is that I wish all USB issues were this easy to fix. My thanks to @RickC for bringing this one to my attention, and to Nir Sofer for bringing us yet another tiny and capable Windows utility.

Author: Ed Tittel

Ed Tittel is a 30-plus-year computer industry veteran. He’s a Princeton and multiple University of Texas graduate who’s worked in IT since 1981 when he started his first programming job. Over the past three decades he’s also worked as a manager, technical evangelist, consultant, trainer, and an expert witness. See his professional bio for all the details.

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