I have EXACTLY the same problem, precisely after installing the update to iOS 10.3.1. When I took my iPhone 6 w/64GB to the Apple Store, the Genius Bar technicians ran some diagnostics programs on it and apparently nothing was wrong: The only recommendation they gave me to solve the problem they couldn't diagnose was to install the iOS update to 10.3.2, which I did.
So, I've installed that update and after that, I've reset all Network Settings afterwards:he problems remained exactly untouched: Terrible Wi-Fi (I am capable to connect to my Home Wi-Fi Network ONLY if I am practically in front of the Router, not beyond 10 feet) and uncapable to connect to any GPS satellites, even if I am outside in the clear.
I've already done another test: I updated my other iPhone (an iPhone 5S w/16GB) to iOS 10.3.2 and EVERYTHING WORKS FINE. When I put both phones side by side, the iPhone 5S can locate several other Wi-Fi Networks, while the iPhone 6 is able to locate ONLY my Home Wi-Fi...when I am very close to the Router.
Which really infuriates me is the fact that Apple simply do not acknowledges this problem that is happening to many iPhone 6 owners, just when we (stupidly) try to keep our phones updated.
The only alternative that the Genius Bar in the Apple Store gave me was to spend US$350 Dollars to replace my iPhone 6 for another exactly identical. But, besides a stupid cost that I DON'T FEEL WE MUST PAY, who guarantees me that I will not have the same problem with an identical model?
WE NEED TO OBTAIN A RESPONSE FROM APPLE!