I just bought a used 2015 Silverado. Previous owner didn't have a fob. I did some research and determined I could buy a fob and have a locksmith program it for me. I wanted to know if I could get a fob with remote start, so I checked the RPO codes to see if I had AP3 or AP8. Discovered it didn't have any keyless entry codes. Does this mean it's not even capable of having a fob programmed?
TL;DR No, the absence of keyless access codes does not necessarily mean you can't program a fob.
After receiving no answers, I decided to take the plunge. Rather than take it to a locksmith, I bought a product from Doorman that allows you to program them yourself. I honestly didn't expect it to work, but it did! So yeah, I can't speak authoritatively, but in my case, it ended up working out.