The official firmware locks certain diagnostic features. The open-source community has created (e.g., based on B11) that enables:
: In the WebUI under the update section, select the option for a local update and browse for the downloaded file. Essential Precautions Before Updating
If the MF920U is stuck on the logo or not booting, you may need to use a tool called (often referred to as "Download Tool" or "QPST" depending on the chipset).