Adding Outside Temp

My 5 lug 2014 bought new didn't have an outside temperature display, even though I think the brochure at the time said something about the feature being present. I bought one of the Gentex temperature / compass / auto dimming mirrors from some guy on Tacomaworld (I went back and looked and it was Bob's Mirrors), along with the proper trim piece, wiring harness and temperature sensor. Everything in my truck overhead was pre-wired to support it, I think you can tell if you have the sunglasses holders. I took my time with the install using the instructions provided and everything worked as expected and it looks like it came from the factory. I can't figure out why Toyota cheaped out and didn't provide something as basic as outside temperature display on these trucks