Sorry for this late reply.
I've lost my writings for how to upgrade FW on this SDSSDA-240G-G25
As i can remember, the main reason that this dont worked is the fact that the file used was not adapted to my SSD ( firmware dont match and i cant find clear informations how to use this tool).
For mine SSD, i used this file : SM2246XT_MP_EnhancePageMode_MPQ1102A_DBQ0412_FWQ0927A
1. You need to short circuit ROM pins on the MB
2. Plug the ssd (i use sata ssd adapter USB)
3. Launch sm2246XT_MPTool_Q1102A.exe
4. Lauch start on main page TEST = no errors, all is recognised.
5. I remeber that i go to parameters page and check if size was OK inside bow "Flash select". I try push button AUTO if it wasn't OK.
6. After that, inside same page, i click on "edit config" and try to fullfill serial, vendor model, and most of values that need to be fullfilled.
7. I save config and go to TEST page.
8. I run flash. Be careful : I can remember if you need to remove short-circuit ROM pin or not to do the flash correctly.
The only issue i saw (but not mandatory for great functionning) is that SanDisk Dashboard app dont recognize my SSD as a SanDisk SSD, even all informations inside parameter page have been fullfilled. But SMART values, suface RW tests, speed benchs, all is OK.
So, if you have same SSD, you can try this. If i can find my screenshot, i will post it here.
I hope this can help someone.