It's not a supported configuration -- so it's a fluke that it works with the BIOS set to defaults.

I also have a SSD in the WWAN-port (7490) and it is accessable, if I load the BIOS-defaults. On next boot the BIOS seems to overwrite automatically the settings and the drive is gone. But it appears each time I load the defaults (but only for one boot). In my 7440 this constellation worked, in the 7490 not.

I now try the CCTK and hope I find a setting, which makes it permanently visible.

I think, it should be supported by Dell as a second harddrive, many of our users want to seperate the data physicalls from the system.

Hi Martinws,

Are there any updates for this?

Today I have asked Dell support team and what they replied is:
"there is no secondary port available in order to upgrade the second SSD"

Hooray, Dell supports a second SSD in WLAN-Port on the new 7400. I think, that it depends on a BIOS-bug, because the technical support said, that it was not designated for the 7490, so I saved my latest BIOS 1.5.4 for a possible downgrade :-).

Hi, for new 7400, do you know if it's m.2 2230 or 2242 and maximum capacity supported by the WWAN port?

I was also looking to see if the WWAN slot on my E5250 would accept a SSD drive. I found this YT vid 

https://www.youtube.com/watch?v=l92BxOz4WbY&t=301s

He using a Toshiba RC100-M22242-240G SSD Speicherkarte 240GB M.2 PCIe He also makes the point not to use a SATA SSD but the NVMe type, is this correct?? 

Latitude 7400 does support second SSD in WWAN slot. Tested toshiba and liteon NVME 2242 256G, works like a charm

I was able to get a M.2 2242 B+M key WDC SN520 to work fine in the WWAN slot of my 7390.

Do you mind to share the BIOS for your 7390? I have tried to add M.2 2242 into a Dell latitude 7390 and BIOS can't recognizes.

Thanks!

John