Sierra EM7455 device disconnecting/resetting automatically

Hi Guys

I have a Sierra EM7455 Dell branded WWAN modem which I successfully rebranded to Lenovo.

It was working fine for more than 6 months without any issues. It is running on the latest Sierra generic firmware. From last week, the device has been disconnecting (not sure if it being reset) at random intervals. Is it dying? Can it reset if the signal strength is too low or if it is getting hot? I get only 3 to 4 signal bars where as in my phone I have full bars (same network operator).

Please advice how to troubleshoot this problem? I can share the output of your commands from both Windows/Linux OS’s if required.


if you plug to linux, in dmesg , you can check whether the USB has been disconnect and re-connect

Thanks for your reply.

I took this dump after a disconnection, does it make any sense to you?


Seems to be qualcomm stack crash …

You can have a try on a future release later on Release 29

Hi jyijyi

Thanks for that info. Where can I read up more about this Qualcomm stack crash? So you say it is a software/firmware issue rather than a hardware issue?


i saw the C file.
Just my guess tat this is fixed in future release.
You need to test it later.

I updated the firmware to the latest version and voila, the issue was gone.