What does macOS kernel return 0xE0004006 (kIOUSBPIDCheckErr) mean?

 
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kIOUSBDataToggleErr kIOUSBWrongPIDErr

kIOUSBPIDCheckErr

The packet identifier itself could not be trusted

kIOUSBPIDCheckErr means that the USB stack could not validate the packet identifier before it could safely classify the packet. A USB PID contains an identifier nibble and a complementary check nibble. This is separate from the CRC5 and CRC16 mechanisms used for token and data fields, even though older IOUSBFamily wording may describe the condition as a PID CRC error.

The distinction matters for diagnosis. With kIOUSBWrongPIDErr, a PID was readable but did not match the transaction phase the host expected. With kIOUSBPIDCheckErr, the PID's own check fails, so higher layers cannot reliably decide which kind of packet was received. It should not be interpreted as an application-level request-format failure.

Useful diagnostic boundaries

  • Capture the endpoint, direction, speed, controller and hub path, then correlate the result with a USB analyzer trace or controller logs when available.
  • Record whether the error is isolated to one endpoint or accompanies CRC and bit-stuffing errors across several endpoints. A mixed pattern is stronger evidence about the transport path than any single return code.
  • Compare a direct-port run and a different cable or hub path before changing device protocol logic. The PID is checked at the packet-recognition layer, before that logic interprets the payload.
  • Do not treat a successful reconnect as proof that the transaction completed. Re-enumeration restores a device relationship but does not reconstruct which command, if any, reached the function.

Why transfer context is still required

macOS distinguishes control, interrupt, bulk, and isochronous transfer behavior. Retrying and recovery expectations differ by transfer class, so logs should include the class and endpoint rather than storing only this numeric IOKit result.

References

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