but it did not succeed for me - my laptop does not read the USB. Like the guide says, I did have to hold the right arrow key and then insert the power cord to get the laptop into BIOS recovery mode. Another thing that you should do is to download the "Andy P (MDL) Phoenix-Insyde-EFI SLIC Tool" that the guide links to. Running that tool and pointing it to the .hdr file dumped out from the BIOS update executable told me that my recovery filename is CS_A06, not VAUB0A6 like the guide says.
Used XPS12's are around $4-500 on Ebay, while a motherboard replacement is about $270. I'm trying to decide whether to buy a new motherboard and swap it in, versus simply buy a new laptop. I used Dell laptops all through college and beyond for over 14 years now. They make good laptops and I'll still keep buying them. Good luck to anyone out there with this problem.