If my 2017 Toyota Corolla does not have led mirrors and I want to put LED mirrors on the Corolla is the wire harness already there to accept LED mirrors from the factory.
Most likely NO. You can check, but typically when a car is built, it is built to a specific option level at the factory, and that includes the wire harness. The wire harness is not "universal", i.e. built for ALL options, whether they are included on the car or not. Rather they are specific to that car's build. You might see SOME additional harness connectors on occasion, but short of seeing the factory's build sheet it's really hard to say what may or may not be present on yours. The main body harness is usually the one that is most specific to a car.