Why does my 2018 Terrain start with the key 20 feet away for the vehicle?

I can start my Silverado over 50 feet away, and even from inside my house. It all comes down to line of site, power of transmitter and receiver and local RF interferences. But on the other side my Equinox will only work within 15 feet and it has to be a straight clear line of site.

Your fob is a transmitter and the receiver is in the vehicle. It's just like being able to listen to a radio station that's miles away from you. The radio station is the transmitter and your radio is the receiver. Hope that helps! Jim