Sometimes the diagnostic port is hidden. You may need to send an AT command to enable the DM port:
Before reading this guide, you must understand that changing the IMEI (International Mobile Equipment Identity) of a cellular modem is illegal in many jurisdictions (including the USA, UK, EU, and China) if done to bypass tracking, evade carrier blacklists, or cover up stolen hardware. This article is for educational purposes only —specifically for developers testing prototype hardware, resetting development modules to default, or cloning a legally owned IMEI from a damaged module to a replacement under the same license agreement. Proceed at your own risk. quectel ec25 change imei