Here is the BoardDiag v2.99a tool that you can use to recover/unbrick your LG device.
In this package, You can find Boardiag Tool, BoardDiag Manual and etc. You can also find all Supported files for following Devices:
D1L (MSM8960 L,V)/
D1L (MSM8960 S,K,D,A)/
D1L (MSM8960 SKDA DDR8G)/
W3 W5 (MSM8210)/
W3 W5 (MSM8610)/
W7 G2MDS (MSM8226)/
To find out if your phone’s model is supported, please download this file from Google.com, Search your phone’s model number and check the Marketing Name and device in above file.
Your phone is G Vista and Its Model number is D631, You can find that the device entry is “B2L”. The B2 device is supported, So you can use this BoardDiag tool to unbrick your LG G Vista.
For more instructions, please download BoardDiag v2.99a user guide from below link: