If it hasn't already, a faulty fan (and internal dust, plus a dried out pair of heatsink pads) can very easily lead to GPU failure.  You will first need to replace the faulty fan -- and do an internal cleaning and replace the thermal pads under the heatsinks.  Until then, the system absolutely should not be used.  
I know this is a long read, but I hope I get a few responses - thank you.  I have owned my Dell XPS 15 9570 for two and a half years now, and it looks like it's nearing the end of its useful life. The battery's condition degraded drastically a few months ago, from its original 8 to 9 hours of charge to around 1.5 to 2 hours. It wasn't a big deal at first as I could simply get a replacement battery, but as the weeks went by, maintaining the laptop seemed to be a far more expensive endeavor as greater hardware defects than I had anticipated began to surface.After a night of screening a few shows on my TV through the HDMI switch on the Dell, the laptop screen suddenly went offline and turned to black after unplugging the connection; but strangely the fan and backlit keyboard remained operational. This had only happened a few times in the previous years when I would wake up the laptop from sleep, and the only solution was to perform a power reset. I followed the same procedure here, but the machine launched into a boot loop instead.Following several hours of fruitless troubleshooting, I determined that doing a fresh reinstall of Windows 10 on the system was the best course of action. I eventually got the system up and running, and the next step was to configure the NVIDIA graphics card drivers; unfortunately, each attempt to install them terminated in a blue screen of death (BSOD) owed to a failure on "nvlddmkm" (Stop code: PAGE FAULT IN NONPAGED AREA). I performed extensive diagnostic checks using the "ePSA Pre-Boot System Assessment" offered by DELL and received the following error code multiple times: Curiously, this error code would recur on an intermittent basis after every first test whenever I repeated individual tests on the video fan, sometimes generating a detected RPM of less than 2000RPM of the goal for certain tests while also detecting a result within 100RPM of the same target for others - I will probably post a report of that in the comments soon. I think It's interesting to also note that the HDMI connection between the laptop and an external display had been functioning flawlessly during all this until several days ago when it began periodically flickering to a black screen on the secondary display after my latest BIOS update. While doing some research on Google, it seems these issues could be attributable to a dying GPU or a faulty/dusted fan, however, neither of the diagnostic checks I ran indicated a fault with the GPU card itself - I'll share an image in the comments later.  I am yet to disassemble the laptop since I suspect the fans require a thorough cleaning; nevertheless, I am quite anxious that this is a fault owed to a malfunctioning GPU that would necessitate a motherboard replacement or perhaps the purchase of a new laptop altogether. Given everything stated in this article, I would greatly appreciate any input if could this be signs of a dying GPU.
Dying NVIDIA GPU or Faulty Fan?