Name: HTC DIAG Driver
Author: HTC

Question 1

Install fails or stalls?

Accepted Answer

Run the driver installer as administrator and use the correct Windows architecture. If Windows blocks the HTC DIAG driver, check signature requirements or temporarily disable driver signature enforcement, then reinstall.

Question 2

Device not detected?

Accepted Answer

Confirm the phone is in HTC DIAG/diagnostic USB mode, not charge-only or MTP. Use a data-capable cable and check Device Manager for an unknown device or new COM port; try another USB port.

Question 3

Version conflicts/COM port errors?

Accepted Answer

Uninstall older HTC Sync, HTC USB, or Qualcomm diagnostic drivers, remove stale COM ports in Device Manager, reboot, and install only the HTC DIAG driver.