Quectel EM05-G (LTE module) with ThinkPad T14 Gen4 on Fedora 39 and 40

·2 min·Andreas Haerter·Jürgen·

We recently bought a bunch of Lenovo ThinkPad T14 Gen4 Model 21HDCTO1WW. They were shipped with a Quectel EM05-G WWAN module. To our surprise, ModemManager did not activate the module right away even though the Fedora Linux support for the hardware is known to be good. It turned out that our hardware revision reports with a different USB device ID 2c7c:0313 than previous versions which used 2c7c:030a:

Bus 003 Device 002: ID 2c7c:0313 Quectel Wireless Solutions Co., Ltd. Quectel EM05-G

Therefore, the necessary FCC unlock procedure does not get triggered automatically even though an unlock script for the Quectel EM05-G was already added by Leah Oswald. However, the modem works perfectly fine if you unlock it manually after each reboot:

mmcli -L
sudo mbimcli --device-open-proxy --device="/dev/cdc-wdm0" --quectel-set-radio-state=on

We have opened an upstream issue to fix the problem. If you don’t want to wait so long until a new ModemManager version including the fix arrives on your computer, you can help yourself as follows:

sudo mkdir -p "/etc/ModemManager/fcc-unlock.d/"
sudo chown root:root -R "/etc/ModemManager/"
sudo find "/etc/ModemManager/" -type d -exec chmod 0755 {} +
sudo find "/etc/ModemManager/" -type f -exec chmod 0644 {} +
sudo ln -s -f "/usr/share/ModemManager/fcc-unlock.available.d/2c7c" "/etc/ModemManager/fcc-unlock.d/2c7c:0313"

This creates a symlink to the working FCC unlock script 2c7c for the new USB device ID 2c7c:0313 in your local configuration. Hope that helps.