About MC7750 QDLoader mode


I have some MC7750 lost DM /AT/CNS port,just have the qualcomm QDLoader port in device manager.

I want to know the what’s the possible rootcause about this kind of problem?

How to fix this problem?



If the unit has gone back to the Qualcomm bootloader then it is has suffered some form of catastrophic failure and cannot be recovered through any of the tools that Sierra supply. Essentially you are going to have to RMA this unit back through your commercial channel to have it replaced under warranty.

As to the cause it is very difficult to say what has happened. Typically things that I have seen cause this.

  • Trying to download incorrect firmware for the unit (most common cause).
  • Hardware failure.
  • Some external event i.e. excessive voltages being applied to the unit.




I’ve the same problem for MC7455 when installed on Lenovo X220T running Windows 7 Pro 64 bit. I’ve two (2) MC7455 where shown the same errors, whilst for EM7455 no issues. I bought both from China and would like to know either is there any Qualcomm Tools to flash a bootloader through QDloader Port.



I do realize “firmware update” for Sierra Wireless MC73XX and MC74XX are different where for MC73XX does require “QDLoader Port” in “Device Manager” but it requires “QDLoader Port (COM22)” for MC74XX. I’ve checked when I’ve done “firmware update” for EM7455 where should be the same validations with MC7455, because for all sierra’s mobile datacard are via 'fdt.exe".

The main problem here is only “QDLoader Port (COM22)” was generated inside “Device Manager” for Windows 7 Pro 64 bit without other devices (modem, network, dm, nmea). I tried “fdt.exe” but it always checking for “modem status” and couldn’t proceed further. Any thought from you all and much appreciated on how to ignore modem status ? Otherwise I believe that I have a useless Sierra Wireless MC7455. But I’ve a question why EM7455 doesn’t has the same issues? OR MC7455 is not compatible with Windows 7 ?



I would like to update my comments on MC7455 and believe this device already at “Boot and Hold” state (based on manual specification for MC7455) and I don’t aware about that “very smarter” detector (refer to attach). BUT how to move forward to load that firmware when only “QDLoader Port (COM22)” is established inside “Device Manager” whilst “fdt.exe” is always checking for “modem status” ?. If no other options to move forward then this product LTE-A is “useless”.

errors-detection.rtf (3.19 MB)