The issue did not remain confined to the Pixel 3. Pixel 4 and 5 devices began exhibiting identical symptoms. A Pixel 5 user running LineageOS with an unlocked bootloader reported:

An ASCII string representing the hardware model. Product Revision: The hardware and firmware version.

The diagnostic software bypasses the Android operating system entirely, communicating directly with the primary bootloader (PBL) or secondary bootloader (SBL). 3. CID Retrieval

QUSB_BULK_CID in Device Manager is not an error message you want to see. It represents a critical failure in your smartphone's boot process that has forced it into Qualcomm's Emergency Download Mode. For the vast majority of users, this means a trip to a repair shop, an expensive out-of-warranty replacement, or the purchase of a new device.

Standard unbricking guides often show a device simply listed as QUSB_Bulk . This generic listing means the device is in EDL mode, but the host PC has not yet established which specific programmer it needs. More importantly, it usually means the device is in , which does not check signatures. However, over the last five years, manufacturers (especially Xiaomi, OnePlus, and realme) have locked down EDL mode.

On Windows 10 and Windows 11, you may need to disable Driver Signature Enforcement temporarily to allow the Qualcomm QDLoader driver to bind correctly to the QUSB interface.