What does macOS kernel return 0xE0004001 (kIOUSBCRCErr) mean?

 
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kIOReturnNotFound kIOUSBBitstufErr

kIOUSBCRCErr

Integrity failure at the USB transport layer

kIOUSBCRCErr identifies a failed cyclic redundancy check while the USB stack was processing a transaction. CRC protects the transmitted token and data fields; it is below application framing, file formats, and class-specific commands. A valid-looking request buffer in an application therefore does not rule this condition out, because the error concerns what a USB receiver was able to validate on the bus.

This code should be kept separate from kIOUSBPIDCheckErr. USB protects the packet identifier with its own complement check, while CRC5 and CRC16 protect token and data fields. It is also different from kIOUSBBitstufErr, which concerns serial encoding rather than a failed checksum over a decoded field.

Evidence that makes the result actionable

  • Record the endpoint address, direction, transfer type, requested and completed lengths, negotiated speed, and the parent-hub path. A device name alone loses the part of the topology needed to compare failures.
  • Preserve nearby USB events and controller diagnostics. Apple notes that some host-controller paths can report coarser errors than the underlying device response, so this code is not proof that a particular application request or peripheral firmware routine is the sole cause.
  • Repeat the same operation on a direct port, another known-good cable, and another hub path. A change in that matrix helps distinguish the peripheral from the cable, hub, dock, or controller path.
  • Do not retry a non-idempotent device command blindly. First determine whether the device protocol can establish whether the command was accepted before the transfer failed.

Transfer type matters

macOS documents error detection and retry for control, interrupt, and bulk transfers, while isochronous transfers do not provide that recovery model. Capture the transfer class before interpreting the absence or presence of a retry as evidence about the device.

References

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